Vulnerability · Published Sep 4, 2026 · Assigned by openjs
CVE-2026-85184@fastify/middie vulnerable to path-scoped middleware bypass via absolute-form request target
Critical 9.1
In plain English
A critical-severity security flaw in @fastify/middie from @fastify/middie. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 45% of all known vulnerabilities).
Official 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 (as reported)
| Vendor | Product | Versions |
|---|---|---|
| @fastify/middie | @fastify/middie | 9.1.0 – before 9.3.4 |
Weakness: CWE-436 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N