CVE-2025-66491
5.9 · MEDIUMOverview
CVE-2025-66491 is a medium-severity vulnerability affecting traefik traefik. It was published on December 9, 2025 and has a CVSS 3.1 base score of 5.9 (MEDIUM).
This vulnerability has a CVSS 3.1 base score of 5.9, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical Description
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 backend TLS certificate verification) actually disables verification, allowing man-in-the-middle attacks against HTTPS backends when operators believe they are protected. This issue is fixed in version 3.6.3.
Remediation
Check the references section for vendor advisories and patches from traefik. Update traefik to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| traefik | traefik | >= 3.5.0, < 3.6.3 | Affected |
Frequently Asked Questions
What is CVE-2025-66491?
CVE-2025-66491 is a medium-severity vulnerability affecting traefik traefik. It was published on December 9, 2025 and has a CVSS 3.1 base score of 5.9 (MEDIUM).
How severe is CVE-2025-66491?
This vulnerability has a CVSS 3.1 base score of 5.9, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2025-66491?
Check the references section for vendor advisories and patches from traefik. Update traefik to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2025-66491?
CyberStrike's AI-powered security agents can automatically detect CVE-2025-66491 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
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