Use-after-free vulnerability in the substr_replace function in PHP 5.3.6 and earlier allows context-dependent attackers to cause a denial of service (memory corruption) or possibly have unspecified other impact by using the same variable for multiple arguments.
https://exchange.xforce.ibmcloud.com/vulnerabilities/66080
http://www.securityfocus.com/bid/49241
http://www.securityfocus.com/bid/46843
http://www.redhat.com/support/errata/RHSA-2011-1423.html
http://www.php.net/archive/2011.php#id2011-08-18-1
http://www.php.net/ChangeLog-5.php#5.3.7
http://www.mandriva.com/security/advisories?name=MDVSA-2011:165
http://support.apple.com/kb/HT5130
http://openwall.com/lists/oss-security/2011/03/13/9
http://openwall.com/lists/oss-security/2011/03/13/3
http://openwall.com/lists/oss-security/2011/03/13/2
http://marc.info/?l=bugtraq&m=133469208622507&w=2
http://lists.apple.com/archives/security-announce/2012/Feb/msg00000.html