CVE-2026-121966

Name of the Vulnerable Software and Affected Versions Traefik versions 2.x through 2.11.59 Traefik versions 3.x through 3.7.15

Description ForwardAuth subrequests and Ingress NGINX auth-url requests are sent through an auth-server connection pool shared by all clients. This behavior exposes connection-bound NTLM or Negotiate authentication, which are protocols used to authenticate users to a server. An unauthenticated attacker can reuse an authenticated connection belonging to another user, obtaining the victim's identity via authResponseHeaders to gain unauthorized access to backends as that user.

Recommendations Update Traefik 2.x to version 2.11.60 or later. Update Traefik 3.x to version 3.7.16 or later.