The ap_proxy_ajp_request function in mod_proxy_ajp.c in mod_proxy_ajp in the Apache HTTP Server 2.2.x before 2.2.15 does not properly handle certain situations in which a client sends no request body, which allows remote attackers to cause a denial of service (backend server outage) via a crafted request, related to use of a 500 error code instead of the appropriate 400 error code.
https://bugzilla.redhat.com/show_bug.cgi?id=569905
http://www.oracle.com/technetwork/topics/security/cpuapr2013-1899555.html
http://www.debian.org/security/2010/dsa-2035
http://www-01.ibm.com/support/docview.wss?uid=swg1PM15829
http://www-01.ibm.com/support/docview.wss?uid=swg1PM12247
http://www-01.ibm.com/support/docview.wss?uid=swg1PM08939
http://svn.apache.org/viewvc?view=revision&revision=917876
http://secunia.com/advisories/40096
http://secunia.com/advisories/39656
http://secunia.com/advisories/39632
http://secunia.com/advisories/39628
http://secunia.com/advisories/39501
http://secunia.com/advisories/39100
http://marc.info/?l=bugtraq&m=127557640302499&w=2
http://lists.opensuse.org/opensuse-security-announce/2010-04/msg00006.html
http://lists.fedoraproject.org/pipermail/package-announce/2010-May/040652.html
http://lists.fedoraproject.org/pipermail/package-announce/2010-April/039957.html
http://lists.apple.com/archives/security-announce/2010//Nov/msg00000.html