AIKIDO-2026-272579
@fastify/middie is vulnerable to Authentication Bypass
91
Critical Risk
This Affects:
@fastify/middieTL;DR
@fastify/middie decides whether to run path-scoped middleware by matching against the raw request target, while the Fastify router resolves an absolute-form request target to its path before dispatching. Because the two layers evaluate different strings, a request using an absolute-form target reaches the route handler while path-scoped middleware such as authentication is skipped. The fix canonicalizes the request target before middleware path matching so both layers evaluate the same path.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and rely on path-scoped middie middleware for access controls.
Background info
@fastify/middie is vulnerable to Authentication Bypass in versions 9.1.0 - 9.3.3.
How to fix this
Upgrade the @fastify/middie library to the patch version.
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