CVE-2026-54763 Traefik: headerField underscore-variant identity spoofing in BasicAuth / DigestAuth / ForwardAuth
Attackers can spoof identity headers via underscore variants in Traefik's auth middlewares, bypassing authentication controls to access protected routes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-54763?
CVE-2026-54763 is a high-severity authentication bypass vulnerability in Traefik Traefik, published on 6 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-54763?
9 open source packages ship an affected version, including github.com/traefik/traefik/v3, github.com/traefik/traefik and github.com/traefik/traefik/v2. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/traefik/traefik/v3 Go | All versions | 3.6.22, 3.7.6 |
github.com/traefik/traefik/v3 Go | All versions | 3.6.22 |
github.com/traefik/traefik/v3 Go | All versions | 3.6.22 |
github.com/traefik/traefik/v3 Go | From 3.7.0 | 3.7.6 |
github.com/traefik/traefik/v3 Go | From 3.7.0 | 3.7.6 |
github.com/traefik/traefik Go | All versions | None |
3 more packages
github.com/traefik/traefik/v2 Go | All versions | 2.11.51 |
github.com/traefik/traefik/v2 Go | All versions | 2.11.51 |
github.com/traefik/traefik/v2 Go | All versions | 2.11.51 |
Products include Traefik Traefik.
How do I fix CVE-2026-54763?
Upgrade github.com/traefik/traefik/v3 to a fixed version for your release line: 3.6.22 or 3.7.6.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-54763 being exploited?
There is no known exploitation of CVE-2026-54763 in the wild and no public exploit code.
Other vulnerabilities in Traefik Traefik
- CVE-2024-45410 HTTP client can remove the X-Forwarded headers in Traefik
- CVE-2026-88877 Traefik v3.7.0 Authentication Bypass via from-to-www-redirect
- CVE-2026-85595 Traefik before v2.11.55 and v3.0.0 through v3.7.10 Authentication Bypass via digestAuth
- CVE-2026-88007 Traefik HTTP/3 Backend NTLM Connection Reuse
- CVE-2026-88009 Traefik: Rootless HTTP/1 request-target routes as "/" but is forwarded verbatim, bypassing path-scoped routing, middleware guards and access logging
Sources
Also known as GHSA-x677-9fxg-v5c5, GO-2026-6211, MINI-5xmp-q2qc-2h34, MINI-p6f8-r3f5-4pfp, MINI-q6mh-hqhr-h6cp.