CVE-2026-54763: Traefik: headerField underscore-variant identity spoofing in BasicAuth / DigestAuth / ForwardAuth
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 Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in v2.11.51 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in v3.6.22 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in v3.7.6
Event History
Frequently Asked Questions
What is the severity of CVE-2026-54763?
The severity of CVE-2026-54763 is rated as high with a CVSS score of 7.8.
How do I fix CVE-2026-54763?
To fix CVE-2026-54763, you should update Traefik to versions v2.11.51, v3.6.22, or v3.7.6 or later.
What types of authentication are affected by CVE-2026-54763?
CVE-2026-54763 affects the BasicAuth, DigestAuth, and ForwardAuth authentication methods in Traefik.
What is the risk of CVE-2026-54763?
The risk associated with CVE-2026-54763 includes potential identity spoofing due to mishandling underscore-variant HTTP headers.
When was CVE-2026-54763 published?
CVE-2026-54763 was published on July 6, 2026.