CVE-2026-121966 Traefik before 2.11.60 and 3.7.16 ForwardAuth NTLM/Negotiate Identity Leak

High 7.0 Published 4 Nov 2026 Updated 4 Nov 2026

Exploited in the wild: Not known
Fix: None listed

What is CVE-2026-121966?

CVE-2026-121966 is a high-severity vulnerability in traefik, published on 4 Nov 2026.

Official description

Traefik 2.x before 2.11.60 and 3.x before 3.7.16 sends ForwardAuth subrequests (and, in 3.7, Ingress NGINX auth-url requests) through an auth-server connection pool shared by all clients, exposing connection-bound NTLM or Negotiate authentication. An unauthenticated attacker can reuse another user's authenticated connection, receiving the victim's identity via authResponseHeaders to access backends as that user.

Weakness: CWE-488

Which versions are affected by CVE-2026-121966?

How do I fix CVE-2026-121966?

No fix has been published for CVE-2026-121966 yet. Limit exposure of the affected software until one is available.

Is CVE-2026-121966 being exploited?

There is no known exploitation of CVE-2026-121966 in the wild and no public exploit code.

Sources

Also known as GHSA-6cm8-r9cr-2hc7, GHSA-hrpp-p4fc-wwf8.