Description
Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.43, 3.6.14, and 3.7.0-rc.2, there is a high severity authentication bypass vulnerability in Traefik's ForwardAuth and snippet-based authentication middleware. Traefik's forwarded-header sanitization logic targets only canonical header names (e.g., X-Forwarded-Proto) and does not strip or normalize alias variants that use underscores instead of dashes (e.g., X_Forwarded_Proto). These unsanitized alias headers are forwarded intact to the authentication backend. When the backend normalizes underscore and dash header forms equivalently, an attacker can inject spoofed trust context — such as a trusted scheme or host — through the alias headers and bypass authentication on protected routes without valid credentials. This issue has been patched in versions 2.11.43, 3.6.14, and 3.7.0-rc.2.
INFO
Published Date :
2026-04-30T20:26:26.300Z
Last Modified :
2026-05-04T16:58:14.458Z
Source :
GitHub_M
AFFECTED PRODUCTS
The following products are affected by CVE-2026-39858 vulnerability.
| Vendors | Products |
|---|---|
| Traefik |
|
REFERENCES
Here, you will find a curated list of external links that provide in-depth information to CVE-2026-39858.
