Envoy v1.39.0

Summary of changes

Breaking changes

• build: Envoy now uses Bazel 8. Because Envoy still uses WORKSPACE mode, --enable_workspace and --noenable_bzlmod are required and have been added to .bazelrc; external-repository runfiles now appear directly under the runfiles root.
• build: the Intel DLB connection balancer (envoy.network.connection_balance.dlb) is disabled for all builds due to a broken source archive.
• TLS: enforce_rsa_key_usage is deprecated and ignored; Envoy now always enforces the certificate keyUsage extension.
• TLS inspector: client TLS versions are validated and must be between TLS 1.0 and TLS 1.3 (revertible via envoy.reloadable_features.tls_inspector_enforce_client_tls_version).
• OpenTelemetry tracing: the tracer now honors Envoy's request-entry sampling decision, including overall_sampling, even when propagated trace context or the configured sampler requests sampling. This may reduce exported spans.

Security

• HTTP/2 now counts uncompressed cookies toward header-size and header-count limits (CVE-2026-47774), strengthens PRIORITY/WINDOW_UPDATE flood protection, and adds configurable nghttp2 RST_STREAM rate limits.
• HTTP/3 fixes cover QPACK blocked-decoding denial of service (GHSA-p7c7-7c47-pwch) and inconsistent headers-only content-length handling (CVE-2026-48743).
• Security fixes were added for ext_authz (CVE-2026-47205), ext_proc (CVE-2026-47207), gRPC stats (CVE-2026-47204), internal redirects (CVE-2026-47221), and OAuth2 lifecycle handling (CVE-2026-48090).
• OAuth2 adds AES-256-GCM cookie encryption to address CVE-2026-47775. Migration is opt-in: enable oauth2_use_gcm_encryption, monitor oauth_legacy_cbc_decrypt, then disable oauth2_legacy_cbc_decrypt_compat.
• Additional fixes cover DNS query validation (CVE-2026-48497), JSON nesting limits (CVE-2026-48042), PROXY protocol TLV smuggling (CVE-2026-47692), formatter crashes (CVE-2026-47220), TCP StatsD overflow (CVE-2026-48706), TLS SAN NUL handling (CVE-2026-47778), and Zstd decompression memory exhaustion (CVE-2026-48044).
• New upstream RBAC and dynamic-forward-proxy resolved-address filtering provide CIDR-based protection against SSRF after DNS resolution and host selection.

Dynamic modules

• New extension points: access-log/header formatters, downstream and upstream transport sockets, active health checkers, and stats sinks.
• Cluster load balancers can read host stats, read and write dynamic metadata and filter state, and publish main-thread state to worker-local slots.
• Modules can emit metrics from configuration and background contexts; loading and initialization failures now expose server-wide counters tagged by extension instance.
• Added validation-mode detection, network/listener attribute access, batched header and metadata APIs, effective log-level access, and zero-copy borrowed buffers in the Rust SDK.
• Fixed listener HTTP-callout crashes, watermark initialization, streaming-response re-entry, independent decode/encode continuation, CatchUnwind re-entry, Struct configuration handling, and HTTP/TCP bridge buffer overflow with more than 64 slices.

MCP (Model Context Protocol) and AI protocols

• Added a Wuffs-backed streaming JSON parser for MCP, A2A, OpenAI, Anthropic, and related protocols, with bounded field capture, incremental parsing, no DOM allocation, and duplicate-key detection.
• MCP filtering now exposes processing status, supports configurable duplicate-key rejection, and improves oversized-body behavior for pass-through and rejection modes.
• MCP router adds elicitation and server-to-client request routing, plus lazy per-backend initialization.
• MCP JSON REST Bridge adds per-route tool configuration and locally generated tools/list responses.

HTTP, routing and protocol

• New HTTP filters provide weighted bandwidth sharing and selectable sub-filter chains with per-route configuration.
• HeaderMatcher now evaluates separately supplied header values individually instead of matching only their comma-joined representation (revertible via envoy.reloadable_features.match_headers_individually).
• HTTP inspector uses Balsa by default and now fast-fails invalid non-HTTP method bytes instead of buffering up to 64 KiB.
• Added drain-timeout and maximum-connection-duration jitter to reduce synchronized reconnect spikes.
• Routing gains cluster refresh on retries, weighted-cluster reselection, formatter/CEL-based redirect paths, and mixed literal/variable URI-template segments.
• Fixed connection-pool re-entrancy, connectivity-grid teardown and duplicate-attempt bugs, stale on-demand cluster information, and handling of HTTP/2 or HTTP/3 RST_STREAM(NO_ERROR) after complete responses.

TLS, authentication and authorization

• Added CNSA 1.0/2.0 compliance policies, TLS group formatters for identifying post-quantum key exchange, and suppression of oversized client CA lists.
• QUIC supports opt-in TLS key logging and session-ticket resumption.
• TLS certificate compression via the brotli runtime guard is disabled by default; TLS sockets also gain improved connection-reset reporting.
• OAuth2 adds PRIVATE_KEY_JWT, ID-token forwarding, configurable post-logout redirects, access-token-based cookie lifetime, and safe original-request URI formatting with redirect-domain allowlists.
• BasicAuth supports missing-credential pass-through and authenticated-username metadata; JWT extraction can mark forwarded claims whose signatures were not verified.

DNS, load balancing and upstream

• The unified DNS cluster implementation is enabled by default; equivalent c-ares resolvers can be shared across clusters to support shared qcache.
• DNS clusters gain a minimum TTL refresh floor, while dynamic forward proxy sub-clusters can use DnsCluster configuration and resolved-address CIDR filtering.
• Client-side weighted round robin adds out-of-band ORCA reporting with configurable port, authority, and transport socket matching.
• Least-request load balancing can optionally account for pending requests, with a new per-endpoint pending-request gauge.
• Fixed EDS hostname updates, load reports containing only custom metrics or completed requests, and dynamic-forward-proxy lookup teardown.

Networking and system performance

• Linux deployments gain worker CPU affinity and an SO_REUSEPORT BPF connection balancer for CPU-local connection steering.
• Added a Linux sockmap socket interface for accelerating same-host TCP traffic through eBPF.
• io_uring adds multishot receives, adaptive read buffers, and configurable write backpressure.
• Reverse tunnels gain opt-in GOAWAY-aware draining and replacement; MySQL proxy adds downstream TLS termination with caching_sha2_password mediation.
• Added UDP proxy external authorization, network ext_proc metadata reception, and early external-processor stream closure.

Observability

• New access-log data includes upstream TLS SNI and HTTP/TCP downstream/upstream connection duration points; gRPC access logging adds delivery success/failure counters.
• Added dynamic-module and Wasm programmable stats sinks, OpenTelemetry metric request chunking, endpoint observability names, and default-tag overrides.
• Prometheus scraping and large-scale stat-reference release are substantially faster; /peak_heap_dump exposes tcmalloc's peak heap profile.
• Added process-wide Lua and Wasm VM gauges, single-entry stack traces, and an Envoy-version log-format token.
• Tap now honors configured runtime sampling and reports sampled-out requests/connections.

Rate limiting and configuration

• Rate limiting adds static and dynamic per-descriptor limit overrides, zero-token always-reject behavior, and configurable response-metadata namespaces.
• GCP authentication supports bound access tokens, bound JWTs, and unbound access tokens from the metadata server.
• Added file-backed IP tagging, in-place watched-file modification events, runtime-adjustable fixed-heap limits, health-check HTTP status events, and xDS unsubscribe callbacks.
• Redis proxy adds Redis 7.4 hash-field expiry commands and permits custom commands inside transactions.

Other notable changes and fixes

• Fixed Hickory DNS resolver leaks and use-after-free, file-server cancellation use-after-free, Golang filter re-entry, outlier-detection teardown, missing network namespaces, and asynchronous TLS close handling.
• Fixed RTDS guard removal, VHDS subscriptions, Wasm VM cache invalidation when environment variables change, and upstream Wasm metric scoping.
• Improved UDP proxy attempted-host and address logging, Zipkin timestamp trace IDs, gRPC access-log failure accounting, and health-check event detail.
• Added TCP proxy delayed route selection, drain-close handling, and connection-duration access logging.

Docker images: https://hub.docker.com/r/envoyproxy/envoy/tags?page=1&name=v1.39.0 Docs: https://www.envoyproxy.io/docs/envoy/v1.39.0/ Release notes: https://www.envoyproxy.io/docs/envoy/v1.39.0/version_history/v1.39/v1.39.0 Full changelog: https://github.com/envoyproxy/envoy/compare/v1.38.0...v1.39.0

Signed-off-by: Kateryna Nezdolii kateryna.nezdolii@gmail.com Signed-off-by: Ryan Northey ryan@synca.io Signed-off-by: Jonh Wendell jwendell@redhat.com