Home/CVE/@fastify/static versions 8.0.0 through 9.1.0 decode percent-encoded path separators (%2F) before filesystem resolution,
CVE

CVE-2026-6414

@fastify/static versions 8.0.0 through 9.1.0 decode percent-encoded path separators (%2F) before filesystem resolution,

@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.

MEDIUM · CVSS 5.9 EPSS 0.00016
Monitor
  • No active-exploitation, high-EPSS, or public-exploit signals - routine patching cadence
Sigma rules0 YARA rules0
⬡

Weakness Classification

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

Affected Products & Versions

1
fastify fastify-static>= 8.0.0 and < 9.1.1
▤

Affected Packages

1
Language-ecosystem packages (from OSV) tied to this CVE, with the version that fixes it - the dependency-level detail NVD doesn’t carry.
npm @fastify/static MODERATE fixed in 9.1.1
▣

Scoring & Timeline

5.9
MEDIUM · CVSS v3.1 · ce714d77-add3-4f53-aff5-83d477b104bb
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD16 Apr 2026 · 01:16 PM
CVSS VectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
no
Technical impact
partial
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
🔗

References & Sources

4
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://cna.openjsf.org/security-advisories.htmlThird Party Advisory
https://github.com/fastify/fastify-static/security/advisories/GHSA-x428-ghpx-8j92Vendor Advisory
https://github.com/fastify/middie/security/advisories/GHSA-cxrg-g7r8-w69pNot Applicable
https://github.com/honojs/hono/security/advisories/GHSA-q5qw-h33p-qvwrNot Applicable
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