GitHub Advisoryadvisory · npm

GHSA-x428-ghpx-8j92 @fastify/static vulnerable to route guard bypass via encoded path separators

MEDIUM Published 2026-04-16 Modified 2026-04-16 Official page ↗
Aliases
CVE-2026-6414
Ecosystem
npm
Packages
@fastify/static
Severity
Moderate
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Weaknesses
CWE-177
Reviewed
2026-04-16

Affected packages

• npm @fastify/static: >= 8.0.0, < 9.1.1 → fixed in 9.1.1

Description

Impact `@fastify/static` v9.1.0 and earlier decodes percent-encoded path separators (`%2F`) before filesystem resolution, but Fastify's router treats them as literal characters. This creates a routing mismatch: route guards on `/admin/*` do not match `/admin%2Fsecret.html`, but @fastify/static decodes it to `/admin/secret.html` and serves the file. Applications that rely on route-based middleware or guards to protect files served by @fastify/static can be bypassed with encoded path separators. Patches Upgrade to `@fastify/static` >= 9.1.1. Workarounds None. Upgrade to the patched version.

Related

Alias · CVE (1)

  • CVE-2026-6414 @fastify/static versions 8.0.0 through 9.1.0 decode percent-encoded path separators (%2F) before filesystem resolution, while Fastify's… vulnerability

Weakness · CWE (1)

  • CWE-177 Improper Handling of URL Encoding (Hex Encoding) weakness

References