A timeout detection flaw in the httpd mod_proxy_http module causes proxied response to be sent as the response to a different request, and potentially served to a different client, from the HTTP proxy pool worker pipeline.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/90667/modproxyhttp-timeout.txt
Source: https://packetstormsecurity.com/files/90667/mod_proxy_http-Timeout-Detection.html