1.39.0 (Pending)

Incompatible behavior changes

Changes that are expected to cause an incompatibility if applicable; deployment changes are likely required

• build: The contrib extension envoy.network.connection_balance.dlb (Intel DLB connection balancer) has been disabled at the Bazel layer for all builds and platforms due to a breakage at the source archive.

  See https://github.com/envoyproxy/envoy/issues/45491 for local workarounds.

• tls: The enforce_rsa_key_usage configuration option has been deprecated and ignored. Envoy now always enforces the keyUsage extension in peer certificates. Configurations setting this option to false will no longer have any effect and enforcement will be used.

Minor behavior changes

Changes that may cause incompatibilities for some users, but should not for most

• dns: Runtime guard envoy.reloadable_features.enable_new_dns_implementation is now enabled by default. This activates the new DNS implementation, a merged implementation of strict and logical DNS clusters. It can be temporarily reverted by setting the runtime guard to false.

• dns: When the runtime guard envoy.reloadable_features.dns_cache_distinguish_resolution_timeout is enabled, the dynamic forward proxy DNS cache emits the dns_resolution_timeout response code detail for DNS query timeouts instead of dns_resolution_failure. This allows timeouts, which are transient, to be distinguished from other resolution failures such as NXDOMAIN. The guard is disabled by default.

• golang: Reduced the per-cgo-call mutex acquisition on the Golang HTTP filter by making the has_destroyed_ flag a std::atomic<bool>. CAPI methods whose only Envoy-side work is Filter-owned or runs on the worker thread (setHeader, removeHeader, setTrailer, removeTrailer, addData, injectData, continueStatus, sendLocalReply, setBufferHelper, copyBuffer, drainBuffer, setUpstreamOverrideHost, clearRouteCache, setDynamicMetadata, setStringFilterState) no longer take the mutex, eliminating an uncontended atomic compare-and-swap pair on every such call. The mutex is retained on the CAPI methods that inline-dereference Envoy-stream-owned objects from off-thread (getHeader, copyHeaders, copyTrailers, getIntegerValue, setDrainConnectionUponCompletion) where it serialises against onDestroy to prevent the worker thread from freeing the underlying header map or StreamInfo mid-access, and on the five methods that write to the per-request strValue scratch buffer (getStringValue, getDynamicMetadata, getStringFilterState, getStringProperty, getSecret).

• http: HeaderMatcher when matching a header that has multiple values previously matched against the combined string, e.g. x-role: user and x-role: admin would be matched against user,admin. A rule matching admin would not have matched. Such headers are now matched individually, so a rule matching admin matches, and a rule matching user,admin no longer does. This only affects headers sent as separate entries; a single header line containing user,admin is still matched as one value. The change applies everywhere HeaderMatcher is used (route matching, virtual clusters, rate limits, retry policies, access log filters, health checks, fault injection, JWT auth, OAuth2, Thrift/Dubbo routing, etc.), completing the fix previously applied to RBAC rules (CVE-2026-26308).

  It does not change header matching performed via CEL expressions (e.g. RBAC condition) or via the generic matching API’s header inputs (e.g. HttpRequestHeaderMatchInput), which still observe the comma-concatenated value.

  This behavioral change can be temporarily reverted by setting runtime guard envoy.reloadable_features.match_headers_individually to false. The recommended action is to reconfigure undesirably impacted matchers to fit the new pattern.

• http2: Fixed a vulnerability where HTTP/2 PRIORITY and WINDOW_UPDATE frame flood protection could be bypassed by rapidly opening and closing streams. The protection now scales with the number of active streams rather than cumulative opened streams, and frame usage is retired upon stream closure. This behavioral change can be toggled on or off via the guard envoy.reloadable_features.http2_flood_protection_active_streams.

• http2: The GOAWAY load shed point is fixed to use a graceful two-phase shutdown sequence, to avoid risk to client traffic. This behavioral change can be temporarily reverted by setting runtime guard envoy.reloadable_features.http2_fix_goaway_loadshed_point to false.

• load_balancer: The least request load balancer can now include pending requests (streams queued on a connection pool waiting for a connection to establish) in the per-host load value used for selection. This is disabled by default and can be enabled by setting runtime guard envoy.reloadable_features.least_request_lb_count_pending_requests to true. Also adds a new cluster.<name>.endpoint.<addr>.rq_pending_active per-endpoint gauge.

• router: The upstream transport failure reason (e.g. TLS certificate validation errors) is no longer included in the HTTP response body sent to downstream clients. It remains available in access logs via %UPSTREAM_TRANSPORT_FAILURE_REASON%. This behavioral change can be temporarily reverted by setting runtime guard envoy.reloadable_features.hide_transport_failure_reason_in_response_body to false. This is being changed because in many cases the upstream failure details are inappropriate to send to the downstream client as it discloses too many internal details.

• sockets: Existing io_uring deployments now apply write backpressure by default, so a write can return EAGAIN once the write buffer exceeds write_high_watermark_bytes (128 KiB) and resume at or below write_low_watermark_bytes (16 KiB). The readv-based read buffer also grows adaptively up to 16 times read_buffer_size for large transfers.

• stats: Optimized prometheus stats endpoint. Users should see a roughly 30-40% latency improvement in calls to the endpoint for cases where the scrape results in lots of cluster stats. There should be no visible changes to users, or incompatibilities.

• tap: Implemented the previously-unenforced tap_enabled runtime fractional percent sampling in the HTTP tap filter (per request) and the tap transport socket (per connection). The configured fraction of requests/connections is admitted to the existing match predicate; the remainder is short-circuited before any match state is allocated and increments the new rq_sampled_out (HTTP) or cx_sampled_out (transport socket) stat. Configurations that already set tap_enabled (previously accepted and ignored) will begin sampling on upgrade; this enforcement can be temporarily reverted by setting the runtime guard envoy.reloadable_features.tap_honor_tap_enabled to false.

• tls: Runtime guard envoy.reloadable_features.tls_certificate_compression_brotli is now disabled by default. When disabled, QUIC retains zlib-only certificate compression and TCP TLS performs no certificate compression. It can be re-enabled by setting the runtime guard to true.

• tls: SslSocket now reports ECONNRESET as ConnectionReset by reading the system error code from BoringSSL’s error queue, matching RawBufferSocket behavior. When a connection is closed with ConnectionCloseType::AbortReset, SslSocket also skips the TLS close_notify shutdown so the peer reliably observes a TCP RST instead of racing a graceful close against the reset. This behavioral change can be temporarily reverted by setting runtime guard envoy.reloadable_features.ssl_socket_report_connection_reset to false.

• wasm: Upstream HTTP Wasm filter stats now use the server-wide root stats scope instead of the cluster stats scope, matching downstream HTTP Wasm filter scoping. For a custom counter foo in the wasmcustom namespace, admin /stats output changes from cluster.<cluster_name>.wasmcustom.foo to wasmcustom.foo. Prometheus output changes from envoy_cluster_wasmcustom_foo{envoy_cluster_name="X"} to foo because the leading registered custom namespace is stripped by the Prometheus formatter. Plugins that need per-cluster differentiation should encode the cluster name into the metric name themselves. Can be reverted by setting runtime guard envoy.reloadable_features.upstream_wasm_filter_uses_root_scope to false.

Bug fixes

Changes expected to improve the state of the world and are unlikely to have negative effects

• build: Fixed Illegal ambiguous match error when building contrib targets with --config=aws-lc-fips on aarch64 by restricting the using_aws_lc branch of SELECTED_CONTRIB_EXTENSIONS to linux_x86_64. Mirrors the approach taken by #32382 for boringssl_fips.

• build: Fixed Illegal ambiguous match error when building contrib targets with --config=boringssl-fips on aarch64 by restricting the using_boringssl_fips branch of SELECTED_CONTRIB_EXTENSIONS to linux_x86_64. Mirrors the approach taken by #44661 for aws-lc.

• dns_filter: Fix CVE-2026-48497

  Fix sanity checking of the query name length to avoid abnormal process termination. Use ENVOY_BUG in case sanity check fails.

• dns_resolver: Fixed a UAF in the Hickory DNS resolver where the dispatcher lambda posted by the Rust-thread completion callback captured a raw pointer to the resolver. If the resolver was destroyed before the dispatcher drained the lambda, dereferencing the pointer was undefined behavior. The lambda now captures a std::weak_ptr and locks it before touching the resolver.

• dns_resolver: Fixed a memory leak in the Hickory DNS resolver where ActiveDnsQuery::cancel() did not free the pending query state or decrement the pending_resolutions gauge. Cancelled queries now release their shell object, Rust-side query box, and gauge tick synchronously, matching the contract followed by the c-ares and Apple DNS resolvers.

• dns_resolver: Fixed macOS build failure (#45061) for the Hickory DNS resolver by linking Apple’s SystemConfiguration framework. The framework is required by the system-configuration crate that hickory-resolver pulls in via its system-config feature.

• dynamic_modules: Fixed a buffer overflow in the upstream HTTP/TCP bridge body getters where a request or response body split into more than 64 buffer slices would write past the fixed-size array that the Rust SDK passed to envoy_dynamic_module_callback_upstream_http_tcp_bridge_get_request_buffer and its response counterpart. Added the envoy_dynamic_module_callback_upstream_http_tcp_bridge_get_request_buffer_chunks_size and envoy_dynamic_module_callback_upstream_http_tcp_bridge_get_response_buffer_chunks_size ABI callbacks so the module sizes the slice array before filling it.

• dynamic_modules: Fixed a bug in the HTTP dynamic module filter where the streaming-response callbacks send_response_headers, send_response_data and send_response_trailers re-entered the module’s own encode hooks for the response it was producing. The encode hooks are now suppressed for these responses, matching the behavior of send_response.

• dynamic_modules: Fixed a bug in the HTTP filter where the decode and encode directions shared a single continue flag, so a request body that continued the decode direction while an upstream response was held at encodeHeaders turned the later continueEncoding() into a silent no-op and wedged the held response. Because the flag was shared, one resume could never continue both directions. The decode and encode continue states are now tracked independently so a continue in one direction never suppresses a resume in the other.

• dynamic_modules: Fixed a bug where the HTTP filter per-route configuration and the upstream HTTP TCP bridge configuration did not handle the google.protobuf.Struct configuration message as the API definition requires. Both factories now serialize the Struct to a JSON string and pass the string to the dynamic module side as the configuration, matching the behavior already in place for every other dynamic module extension factory.

• dynamic_modules: Fixed a crash in the listener dynamic module filter where a module that issued an HTTP callout aborted the worker. The callout path called shared_from_this on a filter that was not shared owned, which threw std::bad_weak_ptr. The filter is now held by a shared_ptr so the async callout and scheduler paths work.

• dynamic_modules: Fixed a crashing bug in the HTTP filter when a stream was already above the downstream write-buffer high watermark at filter-chain construction time. Downstream watermark callback registration is now deferred until the in-module filter has been constructed.

• dynamic_modules: Fixed undefined behavior in dynamic modules wrapped with CatchUnwind if the filter was reentered during a callback (e.g., on_stream_complete being invoked inline when responding with end-of-stream from on_scheduled). The filter is now borrowed instead of taken when checking for poison.

• ext_authz: Fix: CVE-2026-47205

  Fixed a use-after-free crash in the ext_authz filter when per-route service overrides are active and the downstream connection resets during an in-flight authorization check.

• ext_proc: Fix: CVE-2026-47207

  Fixed a bug when the ext_proc server sends packed unexpected ProcessingResponses to Envoy.

• ext_proc: Fixed a bug in the ext_proc HTTP filter where a failure to create the gRPC client for the external processor caused Filter::openStream() to short-circuit to IgnoreError regardless of failure_mode_allow. The underlying ProcessorClientImpl::start() returned nullptr without invoking onGrpcError/onGrpcClose, so the consuming filter could not distinguish a client-creation failure from a successful no-op. The client now reports the failure via onGrpcError with status INTERNAL so the consuming filter applies the configured failure_mode_allow semantic. This behavior can be temporarily reverted by setting envoy.reloadable_features.ext_proc_report_client_creation_error to false.

• file_server: Fixed a use-after-free in the file_server HTTP filter when a request is cancelled (downstream RST, stream timeout, etc.) before the underlying AsyncFileManager::stat or read callback fires. FileStreamer previously captured [this] into the async-file callbacks, which left a dangling pointer if the FileStreamer was destroyed while a stat or read was still in flight or already queued on the owner dispatcher. The callbacks now use cancelWrapped (source/common/common/cancel_wrapper.h): the in-flight file operation is aborted via the file-side cancel, and any callback already dispatched to the worker’s event loop short-circuits before dereferencing the freed FileStreamer.

• formatter: Fix: CVE-2026-47220

  Fixed a crash bug in the %REQUESTED_SERVER_NAME% formatter where the host or original host is not set correctly but the formatter is configured to access the host value.

• golang: Fixed a crash in the Golang HTTP filter introduced by #44503 where continueStatus or sendLocalReply invoked synchronously from inside a Go OnHttpHeader/OnHttpData cgo callback would re-enter the C++ state machine while the cgo frame was still on the stack, tripping the ASSERT(filterState() == Processing*) at the top of handle*GolangStatus once the cgo call returned. The inline-on-worker-thread optimization from #44503 is reverted for these two CAPI methods; both now always post to the dispatcher, matching the pre-#44503 behavior.

• grpc_stats: Fix: CVE-2026-47204

  Fixed a crash or use-after-free when gRPC stats filter performs stat tracking on a direct response route.

• http: Fixed a bug in the HTTP connection pool grid where, when starting with HTTP/2 (e.g., HTTP/3 is disabled or broken) and the TCP connection fails, a redundant second TCP connection attempt was scheduled instead of immediately propagating the failure. This behavior can be temporarily reverted by setting the runtime flag envoy.reloadable_features.connectivity_grid_prevent_double_h2_scheduled to false.

• http: Fixed a bug where an upstream HTTP/2 or HTTP/3 RST_STREAM(NO_ERROR) received after a complete response would cause the response to be discarded and replaced with an error. This behavior is common with some gRPC clients and servers, but is often intermittent. This behavior can be temporarily reverted by setting the runtime flag envoy.reloadable_features.http_preserve_rst_no_error to false.

• http: Fixed a bug where subsequent HTTP filters in the chain did not have access to up-to-date cluster information after successful on-demand cluster discovery. The route cluster is now automatically refreshed.

• http: Fixed a re-entrancy bug in the connection pool where attaching a pending stream to a ready connection could recursively trigger connection allocation and ready callbacks if the stream was synchronously reset. This is resolved by removing the pending stream from the queue before calling its initialization/ready callback. This behavior can be temporarily reverted by setting the runtime flag envoy.reloadable_features.conn_pool_fix_reentrancy to false.

• http: Fixed a use-after-free and virtual method call crash in the connectivity grid during teardown when connection attempts are still active. This fix can be temporarily disabled by setting runtime feature envoy.reloadable_features.conn_pool_grid_early_return_on_teardown to false.

• http2: Fix: CVE-2026-47774

  HTTP/2 streams will now be reset if the stream violates the maximum header list size configured via mutable_max_request_headers_kb. Note that this is different than the per header size specified by max_header_field_size_kb. Uncompressed cookies now count towards this limit to protect Envoys against large uncompressed cookies causing excessive memory usage. Additionally, cookies now also count towards max_headers_count limits. This behavior can be reverted by setting the runtime guard envoy.reloadable_features.http2_include_cookies_in_limits to false.

• json: Fix: CVE-2026-48042

  Limit JSON nesting depth at 1000. The limit could be relaxed to 10K by setting the envoy.reloadable_features.limit_json_parser_nesting_depth to false.

• load_report: Fixed a bug in load stats reporting where reports were dropped if only custom metrics or completed requests were present in a reporting interval. This behavioral change can be reverted by setting the runtime guard envoy.reloadable_features.report_load_for_non_zero_stats to false.

• mcp: Transitioned the JSON parser to complete parsing of the root object, removing the early-stopping optimization to mitigate JSON Parameter Pollution (JPP) vulnerabilities.

• oauth2: Fix: [CVE-2026-48090](https://github.com/envoyproxy/envoy/security/advisories/GHSA-3cj2-c63f-q26f)

  Fixed a bug where the asyncronous token change callback could be triggered after the filter had been torn down (onDestroy() had been called), which could lead to access dangling pointers and result in UAF/crash.

• oauth2: Fix: CVE-2026-47775

  Addressed a padding oracle in the OAuth2 filter’s AES-256-CBC cookie decryption. The filter now supports AES-256-GCM encryption with a gcm. algorithm marker, which authenticates the ciphertext and removes the oracle.

  The fix is opt-in to keep rolling upgrades safe. On upgrade, the default behaviour is unchanged: cookies are still encrypted with AES-256-CBC and the CBC decrypt path is still reachable, so existing sessions and mixed-version clusters keep working. Two runtime flags control the migration:

  • envoy.reloadable_features.oauth2_use_gcm_encryption (default false) — when set to true, encrypt() produces AES-256-GCM ciphertexts prefixed with gcm.. While false (the default), encrypt() continues to emit AES-256-CBC ciphertexts with no prefix, wire-compatible with older instances.

  • envoy.reloadable_features.oauth2_legacy_cbc_decrypt_compat (default true) — when true, decrypt() accepts both gcm.-prefixed cookies (via GCM) and legacy cookies (via the legacy CBC fallback). When set to false, only gcm.-prefixed cookies decrypt, legacy CBC cookies are rejected and the affected users are redirected to the OAuth server to re-authenticate. While the CBC fallback is reachable, it partially reopens CVE-2026-47775.

  You should set envoy.reloadable_features.oauth2_use_gcm_encryption to true once you have ensured that all instances in your cluster are capable of decrypting GCM-encrypted cookies. And then, you could set envoy.reloadable_features.oauth2_legacy_cbc_decrypt_compat to false to disable the legacy CBC decryption path at appropriate time.

  Never set ``envoy.reloadable_features.oauth2_legacy_cbc_decrypt_compat`` to ``false`` before you have enabled ``envoy.reloadable_features.oauth2_use_gcm_encryption``.

  Both flags and the AES-256-CBC code paths are scheduled for removal once the migration window has elapsed.

  The OAuth2 filter exposes a new counter oauth_legacy_cbc_decrypt that increments each time a cookie is successfully decrypted via the legacy CBC fallback. Operators should watch this stat decay to zero across the migration window before flipping oauth2_legacy_cbc_decrypt_compat to false.

• oauth2: Fixed a bug where HMAC verification may exposure a timing side channel that leaks information of HMAC secret validity.

• oauth2: Fixed a crash in the OAuth2 filter where AES-CBC decryption of token cookies could spuriously succeed (~1/256) when the configured HMAC secret did not match the secret used to encrypt the cookie (for example after secret rotation, or when receiving legacy unencrypted tokens). The resulting binary “plaintext” was written back into the Cookie: request header and tripped a HeaderString validation assert. Such plaintexts are now rejected and the original cookie value is preserved, matching the behavior already documented for the explicit decryption-failure case.

• proxy_protocol: Fix: CVE-2026-47692

  Fixed a bug where passthrough TLVs combined with added TLVs could exceed the maximum length, resulting in a mismatch between the size reported in the header and the number of bytes written. This could allow a smuggled request from the host writing the PROXY protocol header to the upstream host. This behavioral change can be reverted by setting the runtime guard envoy.reloadable_features.proxy_protocol_remove_too_long_tlvs to false.

• quic: Fix: CVE-2026-48743.

  Validate HTTP/3 headers-only request and response content-length, and reset stream if inconsistent.

  The change is guarded by runtime guard envoy.reloadable_features.quic_validate_headers_only_content_length.

• quic: Fix: GHSA-p7c7-7c47-pwch

  Denial-of-Service Attack Against the HTTP/3 Stack via QPACK Blocked Decoding.

• rbac: Fixed a bug in the mTLS Authenticated principal extension where if an invalid SAN matcher was configured, it would incorrectly match any certificate in the allowed trust chain. Known bad configurations are an invalid OID when using an OTHER_NAME, or specifying a StringMatcher with an invalid configuration.

• router: Fix: CVE-2026-47221

  Fixed an issue when handling HTTP 303 internal redirects for body-less requests. The redirect handling code attempted to drain a request body buffer that was never allocated, causing a segmentation fault.

• router: Fixed a lifetime bug in dynamic forward proxy async host selection when the cluster is removed while lookup is still pending. Pending lookups are now cleaned up on DFP load balancer teardown, and the router no longer resumes async completion through a stale cluster reference.

• runtime: Fixed a bug where removing an RTDS override for an envoy.reloadable_features runtime guard updated the admin runtime view but left the process-wide runtime guard set to the previous overridden value.

• spiffe_validator: Fixed a bug where if an invalid custom SAN matcher was configured it would later lead to a crash when validating a certificate.

• tcp_proxy: Fixed a bug in tcp_proxy where an upstream TCP RST was propagated to downstream even when the HTTP stream had already completed, causing buffered response data to be dropped and the client to receive EOF instead of the response. The RST is now only propagated when the stream was not already complete.

• tcp_statsd_sync: Fix: CVE-2026-48706

  Fixed a TcpStatsdSync buffer overflow issue with large stats name.

• tls: Fix: [CVE-2026-47778](https://github.com/envoyproxy/envoy/security/advisories/GHSA-f8x4-rw5x-f3r7)

  Fixes an issue where Envoy could fail to validate the Subject Alternative Name (SAN) of a peer certificate if the SAN contained an embedded NUL byte. Previously, the SAN parsing was vulnerable to NUL byte truncation in some configurations, potentially leading to incorrect trust decisions.

• tracing: Fixed Zipkin timestamp_trace_ids to encode Unix epoch seconds in the high 32 bits of generated trace IDs, matching the documented [32-bit epoch seconds][32-bit random] format. Previously Envoy used monotonic clock seconds, so the trace ID prefix did not correspond to wall-clock time.

• udp_proxy: Fixed missing attempted upstream host tracking in the UDP proxy tunneling path. TunnelingConnectionPoolImpl now records the upstream host via StreamInfo::UpstreamInfo::addUpstreamHostAttempted on both pool ready and pool failure, so the %UPSTREAM_HOSTS_ATTEMPTED%, %UPSTREAM_HOST_NAMES_ATTEMPTED_WITHOUT_PORT% and related access log formatters are populated for tunneled (UDP-over-HTTP) sessions, matching the behavior of the non-tunneling UDP proxy and TCP proxy.

• udp_proxy: Fixed the UDP proxy not populating the upstream local and remote addresses on the session stream info. As a result the %UPSTREAM_LOCAL_ADDRESS% and %UPSTREAM_REMOTE_ADDRESS% (and their _WITHOUT_PORT / port variants) access log formatters were always empty for non-tunneling UDP -> UDP sessions, unlike TCP proxy. The upstream remote address is now recorded when the upstream host is selected, and the upstream local address once the socket is bound after the first datagram is sent upstream.

• vhds: Fixed a bug where VHDS using a static route configuration wasn’t sending VHDS subscriptions. It should now send subscriptions and also work on-demand.

• wasm: Fixed a bug where Envoy did not recreate the Wasm VM when only environment_variables changed in vm_config. The VM was previously reused from the cache because environment variables were not included in the vm_key computation.

• zstd: Fix: [CVE-2026-48044](https://github.com/envoyproxy/envoy/security/advisories/GHSA-m3p9-47wh-88wg)

  Fixed a memory exhaustion vulnerability in the Zstd decompressor where the MaxInflateRatio limit was only checked after each input slice was fully processed, allowing a maliciously crafted compressed payload to expand to hundreds of MB within a single process() call. The inflate ratio limit is now enforced inside the inner decompression loop, matching the gzip and brotli decompressors and aborting decompression as soon as the threshold is breached.

New features

• access_log: Added %UPSTREAM_SERVER_NAME% access log formatter returning the SNI from the established upstream TLS connection.

• access_log: Supported the singleton stats scope in the stats access logger.

• admin: Added /peak_heap_dump admin endpoint to dump the peak heap profile when tcmalloc is enabled.

• attributes: Added upstream.server_name CEL attribute returning the SNI from the established upstream TLS connection.

• aws_lambda: Added match_excluded_headers and match_included_headers to lambda extension configuration to allow users to exclude specific headers from signing.

• basic_auth: Added allow_missing field to the BasicAuth HTTP filter. When set to true, requests with no Basic credentials (missing or non-Basic Authorization header) are passed through instead of rejected, enabling OR-semantics when combining BasicAuth with other auth filters (e.g. JWT). Invalid credentials are still rejected. Added emit_dynamic_metadata field. When set to true, the filter emits dynamic metadata on successful authentication under the envoy.filters.http.basic_auth namespace with key username, allowing downstream filters (e.g. RBAC) to act on BasicAuth success.

• circuit_breaker: Added support for configuring a budget_interval on the retry budget circuit breaker, allowing new requests to be considered for the duration of the interval when calculating the retry budget. Defaults to 0ms (preserving existing behavior).

• composite: Added support for the inline matcher in the composite HTTP filter. Now users could specify the matcher inline in the filter configuration instead of using the ExtensionWithMatcher filter.

• dns_cluster: Added dns_min_refresh_rate field to DnsCluster. When respect_dns_ttl is enabled, this sets a minimum floor on the TTL-derived refresh interval. DNS records with TTLs shorter than this value will be refreshed at this rate instead, preventing excessively frequent re-resolution for low-TTL records.

• dynamic_forward_proxy: Added resolved_address_filter to the DNS cache config. Resolved addresses matching the configured CIDR ranges are removed from DNS responses, which can be used to prevent the dynamic forward proxy from connecting to internal/private addresses (SSRF protection). Denied addresses are tracked by the new dns_cache.<dns_cache_name>.dns_address_filter_out counter.

• dynamic_modules: Added ABI primitives for publishing main-thread state out to worker threads on the cluster dynamic-module extension: envoy_dynamic_module_callback_cluster_run_on_all_workers (with the matching envoy_dynamic_module_on_cluster_worker_event hook) fans an event out to every registered worker; envoy_dynamic_module_callback_cluster_worker_slot_set / envoy_dynamic_module_callback_cluster_worker_slot_get (with the matching envoy_dynamic_module_on_cluster_worker_slot_data_destroy cleanup hook) publish an opaque payload into a worker thread-local slot and read it back. The Rust SDK adds matching Cluster::on_worker_event, EnvoyCluster::run_on_all_workers, and an EnvoyClusterWorkerSlotExt extension trait with type-safe worker_slot_set<T>(Arc<T>) / worker_slot_get<T>() -> Option<Arc<T>>.

• dynamic_modules: Added envoy_dynamic_module_callback_cluster_lb_context_get_filter_state_bytes and envoy_dynamic_module_callback_cluster_lb_context_get_filter_state_typed ABI callbacks so that a dynamic-module cluster’s load balancer can read filter state set by an upstream HTTP filter (or any other producer) when picking a host. The Rust SDK exposes these as ClusterLbContext::get_filter_state_bytes and ClusterLbContext::get_filter_state_typed.

• dynamic_modules: Added envoy_dynamic_module_callback_http_get_header_values ABI callback that returns all values of a header in a single call, replacing the per-value loop that crossed the ABI boundary and looked up the header once per value. The Rust SDK uses this for EnvoyHttpFilter::get_request_header_values and the response, request trailer, and response trailer variants.

• dynamic_modules: Added envoy_dynamic_module_callback_http_set_dynamic_metadata_string_batch ABI callback that sets multiple string-valued dynamic metadata entries under a single namespace in one call, resolving the namespace and merging into the metadata struct once instead of once per entry. The Rust SDK exposes this as EnvoyHttpFilter::set_dynamic_metadata_string_batch.

• dynamic_modules: Added envoy_dynamic_module_callback_is_validation_mode ABI callback that allows dynamic modules to check if the server is running in config validation mode.

• dynamic_modules: Added a dynamic modules formatter extension (envoy.formatter.dynamic_modules) that allows implementing custom %COMMAND% operators for access logs and header formatting in a dynamic module. The formatter context exposes request, response, and trailer headers, stream info attributes, dynamic metadata, the local reply body, and the access log type. The Rust SDK exposes this through the formatter module and the formatter: arm of declare_all_init_functions!. See DynamicModuleFormatter for configuration details.

• dynamic_modules: Added a new dynamic modules transport socket extension (envoy.transport_sockets.dynamic_modules) that delegates connection I/O to a transport socket implemented in a dynamic module loaded via dlopen. The module performs raw socket reads and writes through io_read and io_write callbacks and transforms the bytes that flow over the connection, for example to implement a custom encryption scheme. The module can also negotiate secure transport for the STARTTLS pattern and inspect the connection’s local and remote addresses. The extension can be configured on both downstream listeners and upstream clusters. The Rust SDK exposes this through a TransportSocket interface and a matching transport socket init function. See DynamicModuleTransportSocket for configuration details.

• dynamic_modules: Added stats sink callbacks that let a dynamic module aggregate metrics off the main thread and publish the results as gauges.

• dynamic_modules: Added support for emitting metrics (counters, gauges, and histograms) from the config context in dynamic modules, enabling metrics to be recorded from background tasks scheduled outside the request, connection, datagram, or log lifecycle. Supported for the HTTP filter (C++, Go, and Rust SDKs), the network and listener filters (Go and Rust SDKs), and the UDP listener filter and access logger (Rust SDK).

• dynamic_modules: Added support for reading the connection.requested_server_name attribute (downstream TLS SNI) from a dynamic module HTTP filter via get_attribute_string. Returns None when no SNI was offered.

• dynamic_modules: Added the envoy_dynamic_module_callback_cluster_lb_context_get_host_stat ABI callback so custom cluster load balancers can read per-host counters and gauges at request time inside envoy_dynamic_module_on_cluster_lb_choose_host. The Rust SDK exposes this as ClusterLbContext::get_host_stat.

• dynamic_modules: Dynamic module extensions now emit counters when loading their configuration fails, so that failures (which are otherwise either only surfaced to the control plane or, for the HTTP filter’s remote fetch path, silently fail open) are observable. The counters are emitted on the server-wide stats scope under the dynamic_modules. prefix (the server scope is used so the counters survive a rejected listener configuration update): module_load_error (the module could not be loaded — missing/invalid source, dlopen failure, by-name lookup miss, or a required ABI symbol could not be resolved), config_init_error (the module loaded but initializing the in-module configuration failed, e.g. on_*_config_new returned null), remote_fetch_error (a remote module source failed to fetch or load, including NACK-mode cache misses; HTTP filter only) and per_route_config_error (a per-route configuration failed to load; HTTP filter only). Each counter carries a config_name tag set to the configured name of the extension instance — for example filter_name, transport_socket_name, lb_policy_name, tracer_name or cluster_name (falling back to default when the extension has no per-instance name, as for the UDP listener filter) — so failures can be attributed to a specific extension instance. The upstreams/http bridge is not yet instrumented because its module is loaded lazily on the data path where no server-wide stats scope is available.

• dynamic_modules: The load balancer, network filter, and listener filter Rust SDK getters return the Envoy-owned buffer directly as a borrowed EnvoyBuffer instead of copying into an owned String, avoiding a per-call allocation on the host-selection and metadata read paths.

• gcp_authn: Added support to fetch and inject bound JWTs from the GCE Metadata Server. Configured via the bound_jwt field in the Audience proto.

• gcp_authn: Added support to fetch and inject bound access tokens from the GCE Metadata Server. Configured via the bound_access_token field in the Audience proto.

• gcp_authn: Added support to fetch and inject unbound Access Tokens from the GCE Metadata Server. Configured via the access_token field in the Audience proto.

• health_check: Added http_status_code field to HealthCheckEjectUnhealthy and HealthCheckFailure proto messages. When the HTTP health checker receives a non-2xx response, the HTTP status code is now populated in health check events. A value of 0 indicates that no HTTP status code was recorded (e.g., network-level failures or non-HTTP health checkers such as TCP, gRPC, Redis, and Thrift).

• http: Added drain_timeout_jitter to HttpConnectionManager. When set, the drain grace period (between the shutdown notice GOAWAY and the final GOAWAY) is extended by a random amount up to drain_timeout * jitter / 100, staggering the final GOAWAY across simultaneously-draining connections to mitigate thundering-herd reconnects.

• http: Added max_connection_duration_jitter to HttpProtocolOptions. When set, the max_connection_duration timer is extended by a random amount up to max_connection_duration * jitter / 100, preventing a thundering-herd of reconnects when many connections are established at roughly the same time. This follows the same pattern as TCP proxy’s max_downstream_connection_duration_jitter_percentage.

• http: Added new filter chain filter to allow users to configure multiple sub filter chain in single position of the main HTTP filter chain. And allow per route configuration of the filter chain filter to select different sub filter chains based on route match criteria.

• http: Added support for the DS_CX_BEG and DS_CX_END COMMON_DURATION time points for HTTP. DS_CX_BEG reflects the downstream connection begin and repeats for all requests on a connection, while DS_CX_END is populated for requests that are active when the downstream connection closes and otherwise renders as "-".

• http: Added the HTTP bandwidth share filter, which provides local fair-sharing of request and response bandwidth across tenants using configurable weights and per-filter-chain or per-route limits.

• http2: Added stream_reset_burst and stream_reset_rate fields to Http2ProtocolOptions. These configure the token-bucket RST_STREAM rate limiter built into nghttp2 (CVE-2023-44487 / HTTP/2 Rapid Reset protection) for server-side connections. The defaults (burst=1000, rate=33/sec) match the existing nghttp2 behavior; operators can raise these limits when legitimate workloads (e.g. gRPC streaming with many short-lived streams that receive RST_STREAM on RESOURCE_EXHAUSTED) exhaust the budget faster than it replenishes. These options only apply when using nghttp2 as a server.

• http2: Added envoy.reloadable_features.http2_max_cookies_size_in_kb runtime value to set the limit on the contents of the re-assembled cookie header. By default there is no limit on the cookie size.

• http2: Added histograms for HTTP/2 header stats, tracking total count of header entries received (including individual cookie headers), total byte size of header map entries, total length of the re-assebled cookie header and total count of individual cookie headers. Histograms are disabled by default and can be enabled by setting the runtime guard envoy.reloadable_features.http2_record_histograms to true. The histograms and the runtime guard will be removed in a future release of Envoy.

• http_inspector: Enabled Balsa parser for HTTP inspector by default. This behavior can be temporarily reverted by setting the runtime guard envoy.reloadable_features.http_inspector_use_balsa_parser to false. This runtime guard will be removed in a future release of Envoy.

• http_inspector: Enabled Balsa parser for HTTP inspector by default. This behavior can be temporarily reverted by setting the runtime guard envoy.reloadable_features.http_inspector_use_balsa_parser to false. This runtime guard will be removed in a future release of Envoy.

• ip_tagging: Added support for loading HTTP IP tagging filter IP tags from a file-based DataSource. YAML and JSON formats are supported, and files are dynamically reloaded when watched_directory is configured on the data source.

• jwt_authn: Added verification_status_header to the ExtractOnlyWithoutValidation requirement. When a JWT is present in the request but fails signature verification, the named request header (default x-jwt-signature-verified) is set to false so downstream filters (RBAC, ext_authz) can distinguish forwarded-but-unverified claims from validated ones. The header is not set on a successfully verified JWT or when no JWT is present. This behavior can be reverted by setting the runtime guard envoy.reloadable_features.jwt_authn_add_verification_status_header to false.

• load_balancing: client_side_weighted_round_robin: implemented out-of-band ORCA load reporting via server-streaming gRPC (xds.service.orca.v3.OpenRcaService.StreamCoreMetrics) when enable_oob_load_report is true. Cluster-scoped stats are emitted under the lb_orca_oob. prefix.

• logging: Added %N as a custom spdlog pattern flag that emits the Envoy version string. It can be used in the --log-format CLI flag or the bootstrap application_log_config.log_format to include the running version in every log line, e.g. --log-format "[%N][%l] %v".

• mcp: Added reject_duplicate_keys config option (defaulting to false) to reject requests that contain duplicate JSON keys at any nesting level.

• mcp: Changed body size limit behavior when the request body exceeds the configured limit. In PASS_THROUGH mode, the request is allowed through with an is_exceeding_limit marker in the dynamic metadata. In REJECT_NO_MCP mode, the request is rejected with a 400 Bad Request if required fields are not found within the limit.

• mcp_router: Added lazy_initialization option to the MCP router filter. When enabled, the initialize response is returned immediately without contacting backends. Each backend is initialized on-demand when a request first routes to it, avoiding slow or misbehaving backends from blocking client initialization.

• mcp_router: Added elicitation support to the MCP router filter. The gateway now transparently handles server-to-client requests (elicitation/create, sampling/createMessage, roots/list) by rewriting JSON-RPC id fields for correct routing in multiplexing mode and forwarding client responses back to the originating backend.

• mcp_transcoder: Added local response handling for the tools/list JSON-RPC method in the MCP JSON REST bridge filter. Configuring tools_list_local will cause the filter to directly generate and serve the available tools list response without sending a request upstream. This may be configured on a per-route basis.

• mcp_transcoder: Added per-route tool config for the MCP JSON REST Bridge filter. If supplied, overrides the main tool config.

• mysql_proxy: Added SSL termination support to the MySQL proxy filter with RSA-mediated caching_sha2_password authentication. The filter can now terminate downstream TLS connections using the starttls transport socket and transparently mediate MySQL 8.0+ caching_sha2_password full authentication by performing RSA public key exchange on behalf of the client. Added a new downstream_ssl config option with DISABLE, REQUIRE, and ALLOW modes.

• network_ext_proc: Added close_stream_to_ext_proc_server to ProcessingResponse to allow the external processor to request closing the gRPC stream early, causing subsequent data to bypass the network ext_proc filter.

• network_ext_proc: Added support for receiving untyped dynamic metadata from the external processing server. Configured via receiving_namespaces.

• oauth2: Added forward_id_token to let the OAuth2 filter forward the OIDC ID token to the upstream on a configurable request header. When the configured header is Authorization the ID token is forwarded using the Bearer `` prefix; for any other header the raw token value is forwarded. When forwarding on a custom header, that header is stripped from the incoming request on every upstream-bound path, including requests bypassed via :ref:`pass_through_matcher <envoy_v3_api_field_extensions.filters.http.oauth2.v3.OAuth2Config.pass_through_matcher>`, so a client can not spoof the forwarded ID token (Envoy only sets it from a validated cookie). Forwarding on the ``Authorization header can not be combined with forward_bearer_token or preserve_authorization_header.

• oauth2: Added original_request_uri to let the OAuth2 filter derive the post-authentication redirect URL encoded in the state parameter from formatter tokens (e.g. %REQ(x-forwarded-proto)%/%REQ(x-forwarded-host)%) instead of from the request’s :scheme and :authority headers. This is useful when Envoy sits behind a gateway that terminates the user-facing hostname, so the post-login redirect targets the public host rather than Envoy’s internal authority. Also added allowed_redirect_domains, a case-insensitive allow-list (exact match or *. wildcard) applied to the host of the formatted redirect_uri, the formatted original_request_uri, and the URL decoded from the OAuth2 state parameter on callback. Requests whose host is not in the list are rejected with 401, mitigating open-redirect attacks via injected x-forwarded-host headers or forged state values. Formatter output that is not a parseable absolute URL is now also rejected with 401 instead of silently passing through. An empty list (the default) disables the check for backward compatibility.

• oauth2: Added use_access_token_expiry_for_id_token_cookie to the OAuth2 filter, allowing the ID token cookie lifetime to be set from the expires_in field of the access token response rather than from the exp claim in the ID token JWT. This is useful when the access token response advertises a longer lifetime than the ID token.

• proxy_protocol: Added encoding option to control how a TLV value is encoded before it is stored in dynamic metadata or filter state. By default the TLV value is sanitized to a valid UTF-8 string (previous behavior). Setting it to BASE64 stores the raw TLV value as a base64-encoded string instead.

• quic: Added support for TLS session ticket resumption in QUIC using configured session ticket keys from session_ticket_keys. This enables faster reconnection across server instances by allowing clients to resume TLS sessions without full handshakes. The feature is disabled by default and can be enabled by setting runtime guard envoy.reloadable_features.quic_session_ticket_support to true.

• ratelimit: Make namespace for storing rate limit service response metadata configurable.

• ratelimit: The HTTP rate limit filter now supports the limit override (including the dynamic_metadata source) when the rate limit configuration is supplied via the filter’s rate_limits field or the per-route RateLimitPerRoute. This allows the per-descriptor limit override and the per-request hits_addend to be used together on the same rule.

• resource_monitors: Overload manager fixed heap resource monitor now supports max_heap_size_bytes_runtime for runtime-overridable max heap size (e.g. RTDS or /runtime_modify).

• router: Added path_rewrite to RedirectAction, a redirect action that constructs the redirect path using substitution format specifiers and CEL expressions, enabling dynamic paths based on request headers, downstream connection attributes, and other stream metadata. Supported in route-level redirects and in the custom response redirect policy.

• router: Added refresh_cluster_on_retry to retry policies so retry attempts can refresh the route-selected upstream cluster before being sent. This enables cross-cluster retries for dynamic cluster selection such as the matcher cluster specifier.

• router: Added support for refreshRouteCluster on weighted cluster routes. When a filter calls refreshRouteCluster(), the weighted cluster entry will select a different cluster from the configured pool, avoiding previously-tried clusters within the same request. Once all clusters have been tried, the selection pool resets so that any cluster may be chosen again. This enables filters to implement per-attempt cluster failover across weighted clusters without replacing the entire route.

• set_metadata_filter: Added per-route configuration support to the set_metadata HTTP filter.

• sockets: The io_uring socket interface now supports multishot reads backed by a kernel-provided buffer ring on Linux kernel 6.0 or later, and applies write backpressure through the new write_high_watermark_bytes and write_low_watermark_bytes options. The readv-based read path now grows its buffer adaptively for large transfers.

• stat_sinks: Added max_data_points_per_request configuration to the OpenTelemetry stat sink to chunk metric export requests.

• stat_sinks: Added a new WASM stats filter contrib extension (envoy.stat_sinks.wasm_filter) that acts as programmable middleware between the metrics snapshot and any inner stats sink. A user-supplied WASM plugin can: filter metrics by index, inject global tags from node metadata (stats_filter_set_global_tags), rename metrics (stats_filter_set_name_overrides), inject synthetic counters/gauges (stats_filter_inject_metrics), and filter histograms (stats_filter_get_histograms). This enables moving centralized metric processing logic (tag enrichment, name rewriting, custom metric injection) into the proxy itself. Configured via WasmFilterStatsSinkConfig.

• stat_sinks: Added a new dynamic modules stats sink extension (envoy.stat_sinks.dynamic_modules) that delegates metric flushing and histogram observations to a dynamic module loaded via dlopen. On each flush the module receives a snapshot of the counters, gauges, and text readouts, plus a callback for every completed histogram sample. Metric names are decoded directly into a module-provided buffer to avoid intermediate allocations. The Rust and Go SDKs expose this through a StatSink interface and a matching stat sink init function. See DynamicModuleStatsSink for configuration details.

• stats: Added observability_name to Endpoint so endpoints can override the observability name used in per-endpoint stats. This allows clusters with duplicate endpoint addresses to expose distinct per-endpoint stats.

• tap: Added configured_sample_rate to the trace wrapper so consumers can recover the sampling rate that was configured when a trace was emitted. Set on the first segment of each tap stream when tap_enabled is configured; absent otherwise.

• tcp_proxy: Added check_drain_close to the TCP proxy filter to close downstream connections with FlushWrite when the drain manager requests drain close during downstream read or write handling.

• tcp_proxy: Added envoy.reloadable_features.tcp_proxy_delay_route_selection to delay selecting a route until just before the upstream connection is established. The selection moment depends on the value of upstream_connect_mode.

• tcp_proxy: Added support for the COMMON_DURATION access log command operator to the TCP proxy. The DS_CX_BEG, DS_CX_END, US_CX_BEG and US_CX_END time points are now populated for TCP connections, which previously rendered as "-".

• tls: Added substitution commands %DOWNSTREAM_TLS_GROUP% and %UPSTREAM_TLS_GROUP%. The TLS group may be used to discern if a TLS connection used a post quantum safe key exchange (e.g. X25519MLKEM768).

• upstream: Added onHostSelected() pre-connection callback to the UpstreamCallbacks interface. Upstream HTTP filters can now inspect the selected host before the upstream connection is initiated and reject the request via sendLocalReply() (for example, to enforce SSRF protection by matching the resolved host address against CIDR deny lists).

• watched_directory: Added watch_modify field to WatchedDirectory. When set to true, the watcher subscribes to Modified (IN_MODIFY) inotify events in addition to MovedTo (IN_MOVED_TO). This allows in-place file writes to trigger reload callbacks, enabling secret managers that write certificate files directly (rather than via atomic rename) to trigger SDS certificate rotation. By default, only move/rename events are watched.