Varnish Cache 7.x < 7.1.2 and 7.2.x < 7.2.1 - HTTP Request Smuggling via Hop-by-Hop Header Handling
An issue was discovered in Varnish Cache 7.x before 7.1.2 and 7.2.x before 7.2.1. A request smuggling attack can be performed on Varnish Cache servers by requesting that certain headers are made hop-by-hop, preventing the Varnish Cache servers from forwarding critical headers to the backend.