Drop Headers via Malicious Connection Header

Vulnerability Description

Traefik is an HTTP reverse proxy and load balancer. Prior to version 2.4.13, there exists a potential header vulnerability in Traefik's handling of the Connection header. Active exploitation of this issue is unlikely, as it requires that a removed header would lead to a privilege escalation, however, the Traefik team has addressed this issue to prevent any potential abuse. If one has a chain of Traefik middlewares, and one of them sets a request header, then sending a request with a certain Connection header will cause it to be removed before the request is sent. In this case, the backend does not see the request header. A patch is available in version 2.4.13. There are no known workarounds aside from upgrading.

References

• https://github.com/traefik/traefik/security/advisories/GHSA-m697-4v8f-55qg
• https://github.com/traefik/traefik/pull/8319/commits/cbaf86a93014a969b8accf39301932c17d0d73f9
• https://github.com/traefik/traefik/releases/tag/v2.4.13