CVE-2026-85184

Description

@fastify/middie versions >= 9.1.0 and before 9.3.4 decide 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 the path-scoped middleware, such as authentication or authorization, is skipped. An unauthenticated network attacker can use this to bypass path-based access controls in a Fastify application that relies on middie for those controls. Users should upgrade to @fastify/middie 9.3.4 or later.

Weakness classification

• ce714d77-add3-4f53-aff5-83d477b104bb: CWE-436

Primary references

• ce714d77-add3-4f53-aff5-83d477b104bb — Third Party Advisory
• ce714d77-add3-4f53-aff5-83d477b104bb — Mitigation, Vendor Advisory