CVE-2025-66491

Aliases:GHSA-7vww-mvcr-x6vjGO-2025-4205CGA-48cp-x3gc-5vwrCGA-4cjx-vgwj-26vjCGA-4pqp-7pr7-h367CGA-5gmp-mfw6-2p3wCGA-83wp-4hvh-g2vjCGA-fvfg-cvmg-59r5CGA-p9qf-8jv9-qpq9CGA-pcp9-ppcr-92q5
Advisory lineage Upstream: 0 Downstream: 3
Analyzed
Published: 09 Dec 2025, 00:38
Last modified:09 Dec 2025, 16:03

Vulnerability Summary

Overall Risk (default)
low
24/100
CVSS Score
5.9 MEDIUM
v3.1 (cve.org)
EPSS Score
0.22% LOW
0% probability +0.21%
KEV
Not listed
Ransomware
No reports
Public exploits
None found
Dark Web
Not detected

Timeline

09 Dec 2025, 00:38
Published
Vulnerability first disclosed
09 Dec 2025, 16:03
Last Modified
Vulnerability information updated

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.

CVSS Metrics

  • v3.1•MEDIUM•Score: 5.9CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS Trends

Current EPSS score: 0.22%• Percentile: 13%

Techniques & Countermeasures

  • CWE-295•Improper Certificate Validation

    The product does not validate, or incorrectly validates, a certificate.

Affected Systems

  • chainguard•traefik-3.5

    all

  • chainguard•traefik-fips-2.11

    < 2.11.51-r0

  • chainguard•traefik-fips-3.5

    all

  • github.com/traefik•traefik

    all

  • github.com/traefik/traefik•v2

    all

  • github.com/traefik/traefik•v3

    ≥ 3.5.0, < 3.6.3

  • traefik•traefik

    ≥ 3.5.0, < 3.6.3

References (6)