Input validation error in Traefik - CVE-2025-66490
Published: December 8, 2025
Vulnerability identifier: #VU119254
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2025-66490
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to bypass implemented security restrictions.
The vulnerability exists due to insufficient validation of user-supplied input processed with using a PathPrefix, Path or PathRegex matcher. A remote attacker can send a specially crafted request with the request path that contains an encoded restricted character from the following set (e.g., '/', '', 'Null', ';', '?', '#') and trick the application into using another router therefore bypassing the middlewares chain.
Affected software
Traefik
How to mitigate CVE-2025-66490
Install updates from vendor's website.
Traefik - addressed in versions 2.11.32, 3.6.3