CVE-2026-33433

Summary

Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.42, 3.6.11, and 3.7.0-ea.3, when headerField is configured with a non-canonical HTTP header name (e.g., x-auth-user instead of X-Auth-User), an authenticated attacker can inject their own canonical version of that header to impersonate any identity to the backend. The backend receives two header entries — the attacker-injected canonical one is read first, overriding Traefik's non-canonical write. Versions 2.11.42, 3.6.11, and 3.7.0-ea.3 patch the issue.

Affected Software

Weaknesses

• CWE-290: CWE-290: Authentication Bypass by Spoofing

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: no
  • Technical Impact: partial

github.com/traefik/traefik: Traefik: Authentication bypass via non-canonical HTTP header injection

Additional References

• https://access.redhat.com/security/cve/CVE-2026-33433
• https://bugzilla.redhat.com/show_bug.cgi?id=2452289
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33433.json
• https://access.redhat.com/errata/RHSA-2026:10175

References

• https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7c
• https://github.com/traefik/traefik/releases/tag/v2.11.42
• https://github.com/traefik/traefik/releases/tag/v3.6.11
• https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3

• ←Previous
• Next→