CVE-2026-41181: Traefik: Errors middleware forwards Authorization and Cookie headers to separate error page service

Severity: medium (CVSS 5.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-05-15 · updated 2026-06-17
Weakness: CWE-201

Description

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.

Affected products

Traefik: before 2.11.44; from 3.0.0 before 3.6.15; 3.7.0-ea1, 3.7.0-ea2, 3.7.0-ea3, 3.7.0-rc1, 3.7.0-rc2 — fixed in 2.11.44, 3.6.15

How to fix

Upgrade to a fixed version: Traefik 2.11.44, 3.6.15. Check the vendor advisory for mitigations.

References

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