CVE-2026-6414

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

Published Apr 16, 2026 CVSS 3.1 · 5.9 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-x428-ghpx-8j92 @fastify/static vulnerable to route guard bypass via encoded path separators
History
Type Values Removed Values Added
CPEs cpe:2.3:a:fastify:fastify-static:*:*:*:*:*:*:*:*
Type Values Removed Values Added
First Time appeared Fastify
Fastify fastify-static
Vendors & Products Fastify
Fastify fastify-static
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title @fastify/static vulnerable to route guard bypass via encoded path separators
Weaknesses CWE-177
References
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
openjs
Published
Updated
Apr 16, 2026, 1:48 PM
Reserved
Apr 15, 2026, 11:37 PM
Status
Analyzed
Published
Apr 16, 2026, 1:16 PM
Modified
Jun 17, 2026, 11:00 AM
Severity
Moderate
Public date
Apr 16, 2026, 1:09 PM