nghttp2: nghttp2: HTTP Request/Response Smuggling and Response-Queue Poisoning via ambiguous HTTP/1.1 Upgrade requests

A flaw in nghttp2's nghttpx proxy allows a remote attacker to perform HTTP request smuggling and cross-client response-queue poisoning. This occurs because the proxy ambiguously forwards HTTP/1.1 Upgrade requests that contain a Content-Length header to reusable keep-alive backend connections...