CVE-2026-22031
Last modified
CVE-2026-22031 is a high-severity vulnerability rated 8.8/10 on the CVSS scale. @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`). EPSS estimates a 0.46% chance of exploitation in the next 30 days.
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.
Metrics
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Fastify | Fastify\/Middie | < 9.1.0 |
References
- https://github.com/fastify/middie/pull/245Issue Tracking, Patch
- https://github.com/fastify/middie/releases/tag/v9.1.0Product, Release Notes
- https://github.com/fastify/middie/security/advisories/GHSA-cxrg-g7r8-w69pExploit, Vendor Advisory
Timeline
- Published
- Last Modified
- Status
- Analyzed
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