The reverse proxy add forward module (mod_rpaf) 0.5 and 0.6 for the Apache HTTP Server allows remote attackers to cause a denial of service (server or application crash) via multiple X-Forwarded-For headers in a request.
https://exchange.xforce.ibmcloud.com/vulnerabilities/77987
http://zecrazytux.net/troubleshooting/apache2-segfault-debugging-tutorial
http://www.securityfocus.com/bid/55154
http://www.openwall.com/lists/oss-security/2012/08/22/7
http://www.openwall.com/lists/oss-security/2012/08/22/2
http://www.debian.org/security/2012/dsa-2532