Description
Traefik is an HTTP reverse proxy and load balancer. Prior to v2.11.51, v3.6.22, and v3.7.6, Traefik's BasicAuth, DigestAuth, and ForwardAuth middlewares strip canonical-cased spoofed identity headers before writing Traefik's own value, but do not account for underscore-variant header names, which many backends normalize identically to dashed forms. An attacker able to reach a protected route can inject an underscore-variant header that survives Traefik's stripping and reaches the backend alongside, or on the unauthenticated ForwardAuth authResponseHeaders path instead of, the value Traefik intended to set, spoofing identity or authorization context. This issue is fixed in versions v2.11.51, v3.6.22, and v3.7.6.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| traefik | traefik | < 2.11.51, >= 3.0.0-beta1, < 3.6.22, >= 3.7.0-ea.1, < 3.7.6 | — |
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.
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 16.0 | govulncheck-vulndb | 0.0.20260827T195228-160000.1.1 | SUSE-SU-2026:23625-1 |
| SLES 16.0 | govulncheck-vulndb | 0.0.20260827T195228-160000.1.1 | SUSE-SU-2026:23625-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | traefik | 3.7.7-1.1 | openSUSE-SU-2026:11251-1 |
| openSUSE Tumbleweed | traefik2 | 2.11.52-1.1 | openSUSE-SU-2026:11243-1 |
| openSUSE Leap 16.0 | govulncheck-vulndb | 0.0.20260827T195228-160000.1.1 | openSUSE-SU-2026:21761-1 |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| Go | github.com/traefik/traefik | all versions | — | GO-2026-6211 |
| Go | github.com/traefik/traefik/v2 | < 2.11.51 | 2.11.51 | GHSA-x677-9fxg-v5c5 |
| Go | github.com/traefik/traefik/v3 | < 3.6.22 | 3.6.22 | GHSA-x677-9fxg-v5c5 |
| Go | github.com/traefik/traefik/v3 | >= 3.7.0, < 3.7.6 | 3.7.6 | GHSA-x677-9fxg-v5c5 |
| Go | github.com/traefik/traefik/v3 | < 3.6.22 · >= 3.7.0, < 3.7.6 | 3.6.22, 3.7.6 | GO-2026-6211 |
Advisories 4
- SUSE-SU-2026:23625-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Sep 29, 2026
- openSUSE-SU-2026:21761-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Sep 9, 2026
- openSUSE-SU-2026:11251-1 traefik-3.7.7-1.1 on GA media SUSE / openSUSE Security Updates · Jul 11, 2026
- openSUSE-SU-2026:11243-1 traefik2-2.11.52-1.1 on GA media SUSE / openSUSE Security Updates · Jul 10, 2026