Traefik: Errors middleware forwards Authorization and Cookie headers to separate error page service

Summary

Traefik is an HTTP reverse proxy and load balancer. Prior to 2.11.44, 3.6.15, and 3.7.0-rc.3, there is an information disclosure vulnerability in Traefik's errors (custom error pages) middleware. When the backend returns a response matching the configured status range, the middleware forwards the original request's complete header set, including Authorization, Cookie, and other authentication material, to the separate error page service rather than only the minimal context needed to render the error page. This behavior is undocumented: the documentation states only that Host is forwarded by default, so operators are not warned that sensitive credentials are shared across service boundaries. Deployments using the errors middleware with a distinct error page service may inadvertently expose end-user credentials to infrastructure that was not intended to receive them. This vulnerability is fixed in 2.11.44, 3.6.15, and 3.7.0-rc.3.

Timeline

1. May 15, 2026, 4:27 PM UTCCVE published
2. May 16, 2026, 1:10 AM UTCCISA SSVC assessment

   Exploitation: none · Automatable: yes · Technical impact: partial

3. May 16, 2026, 1:11 AM UTCRecord last updated

Affected versions

• traefik traefik

  From 3.7.0-rc.0 · fixed in 3.7.0-rc.3; From 3.0.0-beta1 · fixed in 3.6.14; fixed in 2.11.43

• github.com/traefik/traefik/v2Go

  fixed in 2.11.44

• github.com/traefik/traefik/v3Go

  fixed in 3.6.15

• github.com/traefik/traefik/v3Go

  From 3.7.0-rc.0 · fixed in 3.7.0-rc.3

• github.com/traefik/traefikGo

  All versions

• github.com/traefik/traefik/v3Go

  fixed in 3.6.15; From 3.7.0-rc.1 · fixed in 3.7.0-rc.3

References 4