Traefik Vulnerable to BasicAuth/DigestAuth Identity Spoofing via Non-Canonical headerField
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 5.1epss 0.5%
exploitation probability
0.5%top 62% of all CVEs
observed exploitation
nono source reports it
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.
CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N
Affected products
traefik · traefikReferences
https://access.redhat.com/errata/RHSA-2026:10175https://access.redhat.com/security/cve/CVE-2026-33433https://bugzilla.redhat.com/show_bug.cgi?id=2452289https://github.com/traefik/traefik/releases/tag/v2.11.42https://github.com/traefik/traefik/releases/tag/v3.6.11https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7chttps://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33433.json