CVE-2026-33433
Fixed in a distro release EPSS <1%CVSS 5.1
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.
Products: traefik, Red Hat OpenShift Dev Spaces 3.27
Fixed upstream
| Ecosystem | Package | Fixed in |
|---|---|---|
| Go | github.com/traefik/traefik | no fix |
| Go | github.com/traefik/traefik/v2 | 2.11.42 |
| Go | github.com/traefik/traefik/v3 | 3.6.12 |
| Go | github.com/traefik/traefik/v3 | 3.7.0-ea.3 |
Distro releases
| Release | Package | Fixed in |
|---|---|---|
| Chainguard | traefik-2.11 | 2.11.42-r0 |
| Chainguard | traefik-3.5 | no fix |
| Chainguard | traefik-fips-2.11 | 2.11.42-r0 |
| Chainguard | traefik-fips-3.5 | no fix |
| openSUSE Leap 15.6 | govulncheck-vulndb | 0.0.20260402T184258-150000.1.158.1 |
| openSUSE Leap 16.0 | govulncheck-vulndb | 0.0.20260723T184607-160000.1.1 |