Vulnerability · Published Nov 4, 2026 · Assigned by VulnCheck

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

High 8.7

In plain English

A high-severity security flaw in traefik from traefik. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 27% of all known vulnerabilities).

Severity (CVSS 3.1)8.7High

Exploit odds (30 days)0.3%top 73.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

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.

Affected products (as reported)

Vendor	Product	Versions
traefik	traefik	0 – before 2.11.60
traefik	traefik	3.0.0 – before 3.7.16

Weakness: CWE-488 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N

References

GitHub Security Advisory (GHSA-hrpp-p4fc-wwf8) vendor-advisory
VulnCheck Advisory: Traefik before 2.11.60 and 3.7.16 ForwardAuth NTLM/Negotiate Identity Leak third-party-advisory