@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.
Advisories

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Fixes

Solution

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Workaround

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History

Fri, 04 Sep 2026 14:30:00 +0000

Type Values Removed Values Added
First Time appeared Fastify
Fastify fastify/middie
Vendors & Products Fastify
Fastify fastify/middie

Fri, 04 Sep 2026 09:30:00 +0000

Type Values Removed Values Added
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.
Title @fastify/middie vulnerable to path-scoped middleware bypass via absolute-form request target
Weaknesses CWE-436
References
Metrics cvssV3_1

{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: openjs

Published:

Updated: 2026-09-04T09:15:51.216Z

Reserved: 2026-09-03T11:39:08.481Z

Link: CVE-2026-85184

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-04T10:17:13.900

Modified: 2026-09-04T10:17:13.900

Link: CVE-2026-85184

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-04T14:15:07Z

Weaknesses