CVSS 4.0
7.8 highCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:NCVE-2026-54763
High (7.8) in traefik traefik. EPSS 0.2% chance of exploitation in the next 30 days. Fixed in github.com/traefik/traefik/v2 2.11.51.
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.
Severity
CVSS 3.1
10.0 criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N- EPSS
- 0.2% chance of exploitation in the next 30 days; higher than 15% of CVEs (scores of 2026-10-31)
- CWEs
- CWE-178, CWE-290, CWE-345
- Published
- Modified
- Record from
- the NVD, synced
Affected
- traefik:traefik
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-x677-9fxg-v5c5 | 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 |
| GO-2026-6211 | Go | github.com/traefik/traefik | all versions | no fix published |
| GO-2026-6211 | Go | github.com/traefik/traefik/v2 | <2.11.51 | 2.11.51 |
| GO-2026-6211 | Go | github.com/traefik/traefik/v3 | <3.6.22 >=3.7.0 <3.7.6 | 3.6.22, 3.7.6 |