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.
Advisories

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Fixes

Solution

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Workaround

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History

Wed, 16 Sep 2026 14:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 16 Sep 2026 12:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

threat_severity

Moderate


Wed, 16 Sep 2026 09:00:00 +0000

Type Values Removed Values Added
Description 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.
Title fastify vulnerable to Denial of Service via unhandled exception on HTTP/2 trailer responses
Weaknesses CWE-248
References
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: openjs

Published:

Updated: 2026-09-16T14:00:59.305Z

Reserved: 2026-09-15T12:55:43.189Z

Link: CVE-2026-92081

cve-icon Vulnrichment

Updated: 2026-09-16T14:00:53.603Z

cve-icon NVD

Status : Received

Published: 2026-09-16T09:17:10.137

Modified: 2026-09-16T14:17:14.077

Link: CVE-2026-92081

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-09-16T08:52:49Z

Links: CVE-2026-92081 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-09-16T14:30:10Z

Weaknesses