CVE-2026-6414
Medium
Low
Medium
High
Critical
5.9
CVSS Score
Vulnerability 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 Metrics
Common Vulnerability Scoring System
Vector String:
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Attack Vector
N
Attack Complexity
H
Privileges Required
N
User Interaction
N
Scope
U
Confidentiality
H
Integrity
N
Availability
N
References & Resources
-
https://cna.openjsf.org/security-advisories.htmlce714d77-add3-4f53-aff5-83d477b104bb Third Party Advisory
-
https://github.com/fastify/fastify-static/security/advisories/GHSA-x428-ghpx-8j92ce714d77-add3-4f53-aff5-83d477b104bb Vendor Advisory
-
https://github.com/fastify/middie/security/advisories/GHSA-cxrg-g7r8-w69pce714d77-add3-4f53-aff5-83d477b104bb Not Applicable
-
https://github.com/honojs/hono/security/advisories/GHSA-q5qw-h33p-qvwrce714d77-add3-4f53-aff5-83d477b104bb Not Applicable
Severity Details
5.9
out of 10.0
Medium
Weakness Type (CWE)
CWE-177
Improper Handling of URL Encoding (Hex Encoding)
- Description
- The product does not properly handle when all or part of an input has been URL encoded.
- Typical Severity
- Medium
- Abstraction Level
- Variant
Key Information
- Published Date
- April 16, 2026
