Vulnerability in Traefik
CVE-2026-121966
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.7 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/traefik/traefik/security/advisories/GHSA-hrpp-p4fc-wwf8 (vendor-advisory)
- www.vulncheck.com/advisories/traefik-before-2.11.60-and-3.7.16-forwardauth-ntlm… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-121966?
- CVE-2026-121966 is a high-severity vulnerability in Traefik, classified under CWE-488. CVSS score: 8.7/10. Published 2026-11-04.
- How severe is CVE-2026-121966?
- High severity. CVSS v3 base score is 8.7 out of 10.