Bug 2531486 (CVE-2026-88007)

Summary: CVE-2026-88007 github.com/traefik/traefik: Traefik HTTP/3 Backend NTLM Connection Reuse
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: urgent Docs Contact:
Priority: urgent    
Version: unspecifiedCC: sdawley
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw in Traefik's HTTP/3 ConnContext allows unauthenticated remote attackers to bypass authentication on backends using connection-bound NTLM or Negotiate protocols. Missing service.AddTransportOnContext calls lead to shared kerberosRoundTripper transports, enabling attackers to hijack persistent victim backend connections, read victim-only data, and impersonate victims without credentials.
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Description OSIDB Bzimport 2026-09-10 15:00:57 UTC 
Traefik is an open source HTTP reverse proxy and load balancer. From 2.11.0 until 2.11.57 and 3.7.13, the HTTP/3 entrypoint ConnContext does not call service.AddTransportOnContext, so kerberosRoundTripper uses a shared backend transport instead of a transport dedicated to each frontend connection. With HTTP/3 enabled, a backend using connection-bound NTLM or Negotiate authentication, and backend keep-alive, an unrelated client can reuse a backend connection authenticated for a victim, read victim-only data, and act as that victim without the victim credentials. This issue is fixed in 2.11.57 and 3.7.13.