fastify middie up to 9.3.3 access control

Summaryinfo

A vulnerability was found in fastify middie up to 9.3.3 and classified as critical. The impacted element is an unknown function. The manipulation results in access control. This vulnerability is cataloged as CVE-2026-85184. The attack may be launched remotely. There is no exploit available.

Detailsinfo

A vulnerability was found in fastify middie up to 9.3.3. It has been classified as critical. Affected is an unknown code. The manipulation with an unknown input leads to a access control vulnerability. CWE is classifying the issue as CWE-284. The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

@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.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-85184 since 09/03/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1068.

Upgrading to version 9.3.4 eliminates this vulnerability.

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Productinfo

Vendor

• fastify

Name

• middie

Version

• 9.3.0
• 9.3.1
• 9.3.2
• 9.3.3

Website

• Product: https://github.com/fastify/middie/

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