Vulnerability · Published Dec 9, 2025 · Assigned by GitHub_M
CVE-2025-66490Traefik doesn't Prevent Path Normalization Bypass in Router + Middleware Rules
Medium 6.9
In plain English
A medium-severity security flaw in traefik from traefik. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 38% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Traefik is an HTTP reverse proxy and load balancer. For versions prior to 2.11.32 and 2.11.31 through 3.6.2, requests using PathPrefix, Path or PathRegex matchers can bypass path normalization. When Traefik uses path-based routing, requests containing URL-encoded restricted characters (/, \, Null, ;, ?, #) can bypass the middleware chain and reach unintended backends. For example, a request to http://mydomain.example.com/admin%2F could reach service-a without triggering my-security-middleware, bypassing security controls for the /admin/ path. This issue is fixed in versions 2.11.32 and 3.6.3.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/traefik/traefik | no fix listed | GHSA-gm3x-23wp-hc2c |
| Go | github.com/traefik/traefik | no fix listed | GO-2025-4206 |
| Go | github.com/traefik/traefik/v2 | 2.11.32 | GHSA-gm3x-23wp-hc2c |
| Go | github.com/traefik/traefik/v2 | 2.11.32 | GO-2025-4206 |
| Go | github.com/traefik/traefik/v3 | 3.6.3 | GHSA-gm3x-23wp-hc2c |
| Go | github.com/traefik/traefik/v3 | 3.6.3 | GO-2025-4206 |
Affected products (as reported)
Weakness: CWE-436 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
References
- https://github.com/traefik/traefik/security/advisories/GHSA-gm3x-23wp-hc2c x_refsource_CONFIRM
- https://github.com/traefik/traefik/releases/tag/v2.11.32 x_refsource_MISC
- https://github.com/traefik/traefik/releases/tag/v3.6.4 x_refsource_MISC