GHSA-4mh8-r7rc-xpvc

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GHSA-4mh8-r7rc-xpvc

Summary: fastify vulnerable to Denial of Service via unhandled exception on HTTP/2 trailer responses

Details: ### Impact `fastify` crashes with an uncaught `ERR_HTTP2_INVALID_CONNECTION_HEADERS` exception when a route that registers a response trailer via `reply.trailer()` is served over HTTP/2. Fastify unconditionally adds the `Transfer-Encoding: chunked` header when a trailer is set, which is forbidden on HTTP/2, so Node.js throws while serializing the response headers. The exception is not caught and becomes an uncaughtException, terminating the Node.js process. One unauthenticated HTTP/2 request to any route that uses trailers is enough to crash the server, dropping all in-flight requests, and the request can be repeated to keep the process down. Applications are affected only when HTTP/2 is enabled (`http2: true`) and at least one route registers a trailer. HTTP/1.x responses are not affected. ### Patches Upgrade to `fastify` `5.12.5` or later. ### Workarounds Avoid registering response trailers with `reply.trailer()` on routes served over HTTP/2 until upgrading.

References: https://github.com/fastify/fastify/security/advisories/GHSA-4mh8-r7rc-xpvc, https://nvd.nist.gov/vuln/detail/CVE-2026-92081, https://github.com/fastify/fastify/issues/6574, https://github.com/fastify/fastify/commit/ad06a4c3fe8a944a904f38068249b18b8f552e90, https://cna.openjsf.org/security-advisories.html, https://github.com/fastify/fastify, https://github.com/fastify/fastify/releases/tag/v5.12.5