@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.
References
| Link | Resource |
|---|---|
| https://github.com/fastify/middie/commit/d44cd56eb724490babf7b452fdbbdd37ea2effba | Patch |
| https://github.com/fastify/middie/pull/245 | Issue Tracking Patch |
| https://github.com/fastify/middie/releases/tag/v9.1.0 | Product Release Notes |
| https://github.com/fastify/middie/security/advisories/GHSA-cxrg-g7r8-w69p | Exploit Vendor Advisory |
Configurations
History
No history.
Information
Published : 2026-01-19 16:15
Updated : 2026-03-13 14:40
NVD link : CVE-2026-22031
Mitre link : CVE-2026-22031
CVE.ORG link : CVE-2026-22031
JSON object : View
Products Affected
openjsf
- \@fastify\/middie
CWE
CWE-177
Improper Handling of URL Encoding (Hex Encoding)
