Skip to main content

Improper Certificate Validation

CVE-2025-66491

Medium
5.9/10

Summary

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 (MitM) attacks against HTTPS backends when operators believe they are protected. This issue is fixed in version 3.6.3.

  • HIGH
  • NETWORK
  • NONE
  • UNCHANGED
  • NONE
  • NONE
  • HIGH
  • NONE

CWE-295 - Improper Certificate Validation

The authenticity component of a web system stems from the ability to validate “Digital certificates”, which (i) establish trust between two or more entities sharing data over a network; (ii) ensure data at rest and transit is secure from unauthorized access; and (iii) check the identity of the actors that interact with the system. An application with absent or ineffective certificate validation mechanisms allows malicious users, impersonating trusted hosts, to manipulate the communication path between the client and the host, resulting in unauthorized access to data and to the application’s internal environment, and potentially enabling man-in-the-middle attacks.

References

Advisory Timeline

  • Published