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CVE-2025-66491

5.9 · MEDIUM

Traefik is an HTTP reverse proxy and load balancer.

Published Dec 9, 2025CWE-295EPSS 0.22%

Overview

CVE-2025-66491 is a medium-severity vulnerability. 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, patches, and mitigation guidance. 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.

References

GitHubgithub.com/traefik/traefik/commit/14a1aedf5704673d875d210d7bacf103a43c77e4GitHubgithub.com/traefik/traefik/releases/tag/v3.6.3GitHubgithub.com/traefik/traefik/security/advisories/GHSA-7vww-mvcr-x6vj

How CyberStrike helps

Frequently asked questions

What is CVE-2025-66491?

CVE-2025-66491 is a medium-severity vulnerability. 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, patches, and mitigation guidance. 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 is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2025-66491 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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