Bug 2567741 (CVE-2026-121966)

Summary: CVE-2026-121966 github.com/traefik/traefik: Traefik: Unauthorized access via shared authentication connection pool
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: high    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Traefik. The ForwardAuth middleware routes authentication requests through a connection pool shared across all clients, failing to isolate connection-bound authentication protocols such as NT LAN Manager (NTLM) or Negotiate. An unauthenticated remote attacker could exploit this issue by reusing another user's authenticated connection, allowing them to impersonate legitimate users and gain unauthorized access to backend services.
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Description OSIDB Bzimport 2026-11-05 22:22:28 UTC 
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.