CVEvulnerability

CVE-2026-22031

8.8 HIGH Published 2026-01-19 Modified 2026-06-17 Official page ↗
Status
Analyzed
Published
2026-01-19
Last modified
2026-06-17
Assigner
[email protected]
CVSS 3.1 ([email protected])
8.4 HIGH — CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:L
CVSS 3.1 ([email protected])
8.8 HIGH — CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weaknesses
CWE-177

Description

@fastify/middie is the plugin that adds middleware support on steroids to Fastify. A security vulnerability exists in @fastify/middie prior to version 9.1.0 where middleware registered with a specific path prefix can be bypassed using URL-encoded characters (e.g., `/%61dmin` instead of `/admin`). While the middleware engine fails to match the encoded path and skips execution, the underlying Fastify router correctly decodes the path and matches the route handler, allowing attackers to access protected endpoints without the middleware constraints. Version 9.1.0 fixes the issue.

Affected configurations

• fastify fastify\/middie (< 9.1.0)

Related

Weakness · CWE (1)

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

References