CVE-2026-6414

MEDIUM5.9

@fastify/static vulnerable to route guard bypass via encoded path separators

Published Apr 16, 2026

Modified 3 months ago

Details

@fastify/static versions 8.0.0 through 9.1.0 decode percent-encoded path separators (%2F) before filesystem resolution, while Fastify's router treats them as literal characters. This mismatch allows attackers to bypass route-based middleware or guards that protect files served by @fastify/static. For example, a route guard on a protected path can be circumvented by encoding the path separator in the URL. Upgrade to @fastify/static 9.1.1 to fix this issue. There are no workarounds.

References

WEB

https://cna.openjsf.org/security-advisories.html

WEB

https://github.com/fastify/fastify-static/security/advisories/GHSA-x428-ghpx-8j92

WEB

https://github.com/fastify/middie/security/advisories/GHSA-cxrg-g7r8-w69p

WEB

https://github.com/honojs/hono/security/advisories/GHSA-q5qw-h33p-qvwr

ADVISORY

https://www.cve.org/CVERecord?id=CVE-2026-6414

CVSS Analysis