Answer in brief
CVE-2026-92081 records a Medium severity (CVSS 5.9) vulnerability in fastify vulnerable to Denial of Service via unhandled exception on HTTP/2 trailer responses. The current sources do not mark it as known exploited. The current feed maps fastify/fastify (generic), fastify (npm), fastify (npm). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 5.9. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps fastify/fastify (generic), fastify (npm), fastify (npm). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| fastify/fastifygeneric | >=0 <5.12.5 | 5.12.5 |
| fastifynpm | <5.12.5 | 5.12.5 |
| fastifynpm | >=0 <5.12.5 | 5.12.5 |
Published upstream
Sep 16, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 1, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Sep 16, 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.
Quoted source text, attributed separately from HOL analysis.