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CVE-2026-6414

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

Published: Apr 16, 2026Updated: Apr 23, 2026 Sources: CVE List NVDCWE-177
NVD MITRE
5.9CVSSMEDIUM
EPSS Score
0.4%
Top 68.6%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

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.

CVSS Vector Breakdown

AV:NAC:HPR:NUI:NS:UC:HI:NA:N
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:NIntegrity
None
A:NAvailability
None
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Weaknesses

CWE-177

Affected Products

fastify-staticfastify
Library
OSS Libraries / web-framework
@fastify/static@fastify/static
Library
OSS Libraries / web-framework
fastifyoss-projectOSS Librariesaka fastify/middie, fastify-multipart
@fastify/staticoss-projectOSS Libraries

Exploitability

Official Patch Available

References

https://cna.openjsf.org/security-advisories.html
cna.openjsf.org
https://github.com/fastify/fastify-static/security/advisories/GHSA-x428-ghpx-8j92
github.com
https://github.com/fastify/middie/security/advisories/GHSA-cxrg-g7r8-w69p
github.com
and 1 more references View all →

Timeline

Published
Apr 16, 2026
Last Updated
Apr 23, 2026

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