Vulnerability in Traefik
CVE-2025-66491
Traefik is an HTTP reverse proxy and load balancer. Versions 3.5.0 through 3.6.2 have inverted TLS verification logic in the nginx.ingress.kubernetes.io/proxy-ssl-verify annotation. Setting the annotation to "on" (intending to enable backe…
Vulnerability class: Improper Certificate Validation
EPSS: 0.002 (10.6th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N.
Affected products
- Traefik — versions >= 3.5.0, < 3.6.3
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Patch, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2025-66491?
- CVE-2025-66491 is a medium-severity vulnerability in Traefik, classified under Improper Certificate Validation. CVSS score: 5.9/10. Published 2025-12-09.
- How severe is CVE-2025-66491?
- Medium severity. CVSS v3 base score is 5.9 out of 10.