CVE-2026-22031

8.4 HIGH
Published: January 19, 2026 Modified: March 13, 2026
View on NVD

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.

AI Explanation

Get an AI-powered plain-language explanation of this vulnerability and remediation steps.

Login to generate AI explanation

CVSS v3.x Details

0.0 Low Medium High Critical 10.0
Vector String
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:L

References to Advisories, Solutions, and Tools

Patch Vendor Advisory Exploit Third Party Advisory
https://github.com/fastify/middie/pull/245
Source: security-advisories@github.com
Issue Tracking Patch
https://github.com/fastify/middie/releases/tag/v9.1.0
Source: security-advisories@github.com
Product Release Notes
https://github.com/fastify/middie/security/advisories/GHSA-cxrg-g7r8-w69p
Source: security-advisories@github.com
Exploit Vendor Advisory

4 reference(s) from NVD

Quick Stats

CVSS v3 Score
8.4 / 10.0
EPSS (Exploit Probability)
0.1%
27th percentile
Exploitation Status
Not in CISA KEV

Weaknesses (CWE)

Affected Vendors

openjsf