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CVE-2026-22031

CVE-2026-22031 · Fastify Middie Middleware Path Bypass

This page contains facts from public vulnerability sources. Check the original advisory before updating.

@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.

CVSS 8.4 · High · EPSS 0.5% · Fix available

Published
Updated

Stack: node

Affected products and versions

  • middie

    Versions
    • < 9.1.0: Affected

    No fix published

  • @fastify/middie npm

    Affected ranges
    • SEMVER: < 9.1.0

    Update to 9.1.0

Original sources

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