Unrated severityNVD Advisory· Published Sep 4, 2026
@fastify/middie vulnerable to path-scoped middleware bypass via absolute-form request target
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.
Affected products
1Patches
Vulnerability mechanics
References
2News mentions
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