CVE-2026-92081

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

Published Sep 16, 2026 CVSS 3.1 · 5.9 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-4mh8-r7rc-xpvc fastify vulnerable to Denial of Service via unhandled exception on HTTP/2 trailer responses
History
Type Values Removed Values Added
First Time appeared Fastify
Fastify fastify
Vendors & Products Fastify
Fastify fastify
Type Values Removed Values Added
Metrics ssvc

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

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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
openjs
Published
Updated
Sep 16, 2026, 2:00 PM
Reserved
Sep 15, 2026, 12:55 PM
Status
Awaiting Analysis
Published
Sep 16, 2026, 9:17 AM
Modified
Sep 16, 2026, 7:40 PM
Severity
Moderate
Public date
Sep 16, 2026, 8:52 AM