GHSA-X677-9FXG-V5C5 Traefik: Incomplete fix for CVE-2026-33433 + CVE-2026-39858 cross-cohort: headerField underscore-variant identity spoofing in BasicAuth / DigestAuth / ForwardAuth

Summary There is a high severity vulnerability in Traefik's BasicAuth, DigestAuth, and ForwardAuth middlewares. The fix for CVE-2026-33433 stripped canonical-cased spoofed identity headers e.g. X-Auth-User before writing Traefik's own value, but did not account for underscore-variant header names...

Traefik: Cross-user response poisoning via proxied CONNECT on Traefik's shared backend keep-alive pool

Summary There is a critical vulnerability in Traefik's default HTTP reverse proxy that leads to unauthenticated cross-user response poisoning. When a client opens an HTTP/2 or HTTP/3 CONNECT request, Traefik forwards it — body included — to an HTTP/1.1 upstream over a shared net/http.Transport. I...

CVE-2026-54763

A flaw was found in Traefik, an HTTP reverse proxy and load balancer. The BasicAuth, DigestAuth, and ForwardAuth middlewares in Traefik do not correctly treat underscore-variant header names. This allows a remote attacker to inject a specially crafted header that bypasses Traefik's security...

SUSE CVE-2026-54763

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...

Insufficient Verification of Data Authenticity

Overview github.com/traefik/traefik/v2/pkg/middlewares/auth is a Cloud Native Application Proxy. Affected versions of this package are vulnerable to Insufficient Verification of Data Authenticity in the ForwardAuth process when trustForwardHeader is set to false. An attacker can bypass port-based...

Insufficient Verification of Data Authenticity

Overview Affected versions of this package are vulnerable to Insufficient Verification of Data Authenticity in the ForwardAuth process when trustForwardHeader is set to false. An attacker can bypass port-based authorization checks by injecting a crafted X-Forwarded-Proto header over an unencrypte...

CVE-2026-54763

Traefik (HTTP reverse proxy/load balancer) before versions v2.11.51, v3.6.22, and v3.7.6 allows underscore-variant identity spoofing via BasicAuth, DigestAuth, and ForwardAuth middlewares. These middlewares strip canonical header names but don’t account for underscore-variant headers, letting an ...

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...

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...

CVE-2026-54763

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...

PT-2026-56011

Name of the Vulnerable Software and Affected Versions Traefik versions prior to 2.11.51 Traefik versions prior to 3.6.22 Traefik versions prior to 3.7.6 Description Traefik's BasicAuth, DigestAuth, and ForwardAuth middlewares fail to account for underscore-variant header names when stripping...

CVE-2026-52845

A flaw was found in Caddy, an extensible server platform. A remote attacker can exploit a vulnerability in the forwardauth copyheaders functionality. This occurs because Caddy normalizes HTTP headers into Common Gateway Interface CGI variables by replacing hyphens with underscores, allowing a...

DEBIAN-CVE-2026-52845

Caddy is an extensible server platform that uses TLS by default. Prior to 2.11.4, forwardauth copyheaders deletes the exact client-supplied identity header before copying the trusted value from the auth gateway. But when the request later goes through phpfastcgi, Caddy normalizes HTTP headers int...

CVE-2026-52845

Caddy is an extensible server platform that uses TLS by default. Prior to 2.11.4, forwardauth copyheaders deletes the exact client-supplied identity header before copying the trusted value from the auth gateway. But when the request later goes through phpfastcgi, Caddy normalizes HTTP headers int...

CVE-2026-52845

Summary (CVE-2026-52845): Caddy 2.11.x contains a bypass in forward_auth copy_headers where, prior to 2.11.4, the exact client-supplied header was deleted but HTTP header names are later normalized to CGI variables, allowing an underscore alias to collide with a trusted header in FastCGI backends...

CVE-2026-52845 Caddy: FastCGI header normalization bypass in `forward_auth copy_headers`

Caddy is an extensible server platform that uses TLS by default. Prior to 2.11.4, forwardauth copyheaders deletes the exact client-supplied identity header before copying the trusted value from the auth gateway. But when the request later goes through phpfastcgi, Caddy normalizes HTTP headers int...

CVE-2026-52845 Caddy: FastCGI header normalization bypass in `forward_auth copy_headers`

Caddy is an extensible server platform that uses TLS by default. Prior to 2.11.4, forwardauth copyheaders deletes the exact client-supplied identity header before copying the trusted value from the auth gateway. But when the request later goes through phpfastcgi, Caddy normalizes HTTP headers int...

CVE-2026-52845

Caddy is an extensible server platform that uses TLS by default. Prior to 2.11.4, forwardauth copyheaders deletes the exact client-supplied identity header before copying the trusted value from the auth gateway. But when the request later goes through phpfastcgi, Caddy normalizes HTTP headers int...

EUVD-2026-38558

Caddy is an extensible server platform that uses TLS by default. Prior to 2.11.4, forwardauth copyheaders deletes the exact client-supplied identity header before copying the trusted value from the auth gateway. But when the request later goes through phpfastcgi, Caddy normalizes HTTP headers int...

PT-2026-50879

Name of the Vulnerable Software and Affected Versions Apache APISIX versions 2.12.0 through 3.16.0 Description Improper Input Validation in the forward-auth plugin allows an attacker to spoof identity headers by leveraging specific configurations. Recommendations Upgrade to version 3.17.0...