fastify vulnerable to Denial of Service via unhandled exception on HTTP/2 trailer responses
### 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.
GHSA-4mh8-r7rc-xpvc
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: osv:GHSA-4mh8-r7rc-xpvc
fastify
Source reference: /affected/0/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 5.12.5
Source reference:
/affected/0/ranges - Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"ranges": [
{
"type": "SEMVER",
"events": [
{
"introduced": "0"
},
{
"fixed": "5.12.5"
}
]
}
],
"package": {
"name": "fastify",
"purl": "pkg:npm/fastify",
"ecosystem": "npm"
},
"database_specific": {
"source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-4mh8-r7rc-xpvc/GHSA-4mh8-r7rc-xpvc.json"
}
}
]- Related CVEs
- CVE-2026-92081
Source reference:
/aliases
Publisher severity
No explicit severity was provided.
- Event
- #51918 · Revision 1
- Added to Heist Feed
- Publisher date