CVE-2026-85184 @fastify/middie vulnerable to path-scoped middleware bypass via absolute-form request target
Attackers can bypass path-scoped authentication middleware in Fastify applications by using absolute-form request targets, allowing unauthorized access to protected routes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-85184?
CVE-2026-85184 is a critical authentication bypass vulnerability in @fastify/middie, published on 4 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-436
Which versions are affected by CVE-2026-85184?
It affects 1 product.
Products include Fastify Fastify\/Middie.
How do I fix CVE-2026-85184?
No fix has been published for CVE-2026-85184 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-85184 being exploited?
There is no known exploitation of CVE-2026-85184 in the wild and no public exploit code.
Other vulnerabilities in @fastify/middie
- CVE-2026-14198 @fastify/middie vulnerable to authorization bypass via encoded slash in path parameter values
- CVE-2026-6270 @fastify/middie vulnerable to middleware authentication bypass in child plugin scopes
- CVE-2026-22031 Fastify Middie Middleware Path Bypass
- CVE-2026-2880 @fastify/middie has an improper path normalization vulnerability
- CVE-2026-14181 @fastify/middie standalone engine vulnerable to Denial of Service via malformed percent-encoded paths
Sources
Also known as GHSA-hx87-8wv7-pjv8.