CVE-2026-9495 @koa/router has an Access Control Bypass
Attackers can bypass authentication, authorization, or rate limiting by exploiting a flaw where middleware is silently dropped when router prefixes contain path parameters.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-9495?
CVE-2026-9495 is a medium-severity authentication bypass vulnerability in @koa/router, published on 26 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Versions of the package @koa/router from 14.0.0 and before 15.0.0 are vulnerable to Access Control Bypass due to the middleware being silently dropped from the execution chain when the router prefix contains path parameters. Depending on what the skipped middleware was supposed to protect, an attacker could bypass authentication and authorization, evade rate limiting or bypass input sanitization.
Weakness: CWE-284
Which versions are affected by CVE-2026-9495?
2 open source packages ship an affected version, including @koa/router.
| Package | Affected | Fixed in |
|---|---|---|
@koa/router npm | From 14.0.0 | 15.0.0 |
@koa/router npm | From 14.0.0 | 15.0.0 |
How do I fix CVE-2026-9495?
Upgrade @koa/router to 15.0.0 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-9495 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-9495 exists.
Sources
Also known as GHSA-47p6-69vm-vw6v.