CVE-2026-6414

Description

@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.

PUBLISHED Reserved 2026-04-15 | Published 2026-04-16 | Updated 2026-04-16 | Assigner openjs

Problem types

CWE-177: Improper Handling of URL Encoding (Hex Encoding)

Product status

Credits

blakeembrey reporter

mcollina remediation developer

UlisesGascon remediation reviewer

climba03003 remediation reviewer

References

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

github.com/...s/hono/security/advisories/GHSA-q5qw-h33p-qvwr

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

cna.openjsf.org/security-advisories.html

cve.org (CVE-2026-6414)

nvd.nist.gov (CVE-2026-6414)

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