Improper Authentication in Traefik - #VU156702
Published: October 21, 2026
Vulnerability identifier: #VU156702
CSH Severity: High
CVSS v4: 9.1 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-287
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to bypass authentication and access a backend using another client's identity.
The vulnerability exists due to improper authentication isolation in Traefik's ForwardAuth middleware and Kubernetes Ingress NGINX external authentication handling when authentication subrequests use a shared connection pool with connection-bound authentication such as NTLM or SPNEGO/Kerberos Negotiate. A remote attacker can send a request over a separate frontend connection that reuses an authentication-server connection already authenticated by another client to obtain a successful authentication response carrying that client's identity and access the backend as that user.
Affected software
Traefik
Remediation
Install security update from vendor's website.
Traefik - addressed in versions 2.11.60, 3.7.16