CVE-2026-92081 PUBLISHED

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

Assigner: openjs
Reserved: 15.09.2026 Published: 16.09.2026 Updated: 16.09.2026

fastify is a fast and low-overhead web framework for Node.js. In versions before 5.12.5, when a route registers a response trailer via reply.trailer() and is served over HTTP/2, fastify unconditionally sets the Transfer-Encoding: chunked header, which is forbidden on HTTP/2, so Node.js throws while serializing the response headers. The exception is not caught and becomes an uncaughtException, so a single unauthenticated HTTP/2 request to any route that uses trailers crashes the server process and drops all in-flight requests, and it can be repeated on every restart. The issue is fixed in fastify 5.12.5, and users should upgrade to 5.12.5 or later. As a workaround, avoid registering response trailers with reply.trailer() on routes served over HTTP/2 until upgrading.

Metrics

CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS Score: 5.9

Product Status

Vendor fastify
Product fastify
Versions Default: unaffected
  • affected from 0 to 5.12.5 (excl.)
  • Version 5.12.5 is unaffected

Credits

  • mcollina remediation developer
  • UlisesGascon remediation reviewer
  • zerovulnlabs reporter

References

Problem Types

  • CWE-248: Uncaught Exception CWE