Description
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 products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| traefik | traefik | < 2.11.42, >= 3.0.0-beta1, < 3.6.11, >= 3.7.0-ea.1, < 3.7.0-ea.3 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 16.0 | govulncheck-vulndb | 0.0.20260723T184607-160000.1.1 | openSUSE-SU-2026:21483-1 |
| openSUSE Leap 15.6 | govulncheck-vulndb | 0.0.20260402T184258-150000.1.158.1 | SUSE-SU-2026:1205-1 |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| Go | github.com/traefik/traefik | all versions | — | GO-2026-4893 |
| Go | github.com/traefik/traefik/v2 | < 2.11.42 | 2.11.42 | GHSA-qr99-7898-vr7c |
| Go | github.com/traefik/traefik/v3 | >= 3.0.0-beta1, < 3.6.12 | 3.6.12 | GHSA-qr99-7898-vr7c |
| Go | github.com/traefik/traefik/v3 | >= 3.7.0-ea.1, < 3.7.0-ea.3 | 3.7.0-ea.3 | GHSA-qr99-7898-vr7c |
| Go | github.com/traefik/traefik/v3 | >= 3.0.0-beta1, < 3.6.12 · >= 3.7.0-ea.1, < 3.7.0-ea.3 | 3.6.12, 3.7.0-ea.3 | GO-2026-4893 |
Advisories 2
- openSUSE-SU-2026:21483-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Jul 31, 2026
- SUSE-SU-2026:1205-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Apr 8, 2026