PHP before 5.3.9 computes hash values for form parameters without restricting the ability to trigger hash collisions predictably, which allows remote attackers to cause a denial of service (CPU consumption) by sending many crafted parameters.
archives.neohapsis.com/archives/bugtraq/2011-12/0181.html
h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=c03360041
lists.apple.com/archives/security-announce/2012/May/msg00001.html
lists.opensuse.org/opensuse-security-announce/2012-03/msg00013.html
lists.opensuse.org/opensuse-security-announce/2012-03/msg00016.html
marc.info/?l=bugtraq&m=132871655717248&w=2
marc.info/?l=bugtraq&m=133469208622507&w=2
rhn.redhat.com/errata/RHSA-2012-0071.html
secunia.com/advisories/47404
secunia.com/advisories/48668
support.apple.com/kb/HT5281
svn.php.net/viewvc?view=revision&revision=321003
svn.php.net/viewvc?view=revision&revision=321040
www.debian.org/security/2012/dsa-2399
www.exploit-db.com/exploits/18296
www.exploit-db.com/exploits/18305
www.kb.cert.org/vuls/id/903934
www.mandriva.com/security/advisories?name=MDVSA-2011:197
www.mandriva.com/security/advisories?name=MDVSA-2013:150
www.nruns.com/_downloads/advisory28122011.pdf
www.ocert.org/advisories/ocert-2011-003.html
www.oracle.com/technetwork/topics/security/cpujul2012-392727.html
www.redhat.com/support/errata/RHSA-2012-0019.html
www.securityfocus.com/bid/51193
www.securitytracker.com/id?1026473
exchange.xforce.ibmcloud.com/vulnerabilities/72021
github.com/FireFart/HashCollision-DOS-POC/blob/master/HashtablePOC.py