CVE-2026-6414

@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.

Score

CVSS 3.1 5.9 Medium

Status

Analyzed - ce714d77-add3-4f53-aff5-83d477b104bb

Published

2026-04-16

Last modified

2026-04-16

Weaknesses

CWE-177

Affected products

• Fastify-static (Fastify)
• Fastifystatic (Fastifystatic)

References

• https://cna.openjsf.org/security-advisories.html
• https://github.com/fastify/fastify-static/security/advisories/GHSA-x428-ghpx-8j92
• https://github.com/fastify/middie/security/advisories/GHSA-cxrg-g7r8-w69p
• https://github.com/honojs/hono/security/advisories/GHSA-q5qw-h33p-qvwr