zend_hash_del_key_or_index in zend_hash.c in PHP before 4.4.3 and 5.x before 5.1.3 can cause zend_hash_del to delete the wrong element, which prevents a variable from being unset even when the PHP unset function is called, which might cause the variable's value to be used in security-relevant operations.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A10118
https://issues.rpath.com/browse/RPL-683
https://exchange.xforce.ibmcloud.com/vulnerabilities/27396
http://www.turbolinux.com/security/2006/TLSA-2006-38.txt
http://www.securityfocus.com/bid/17843
http://www.securityfocus.com/archive/1/447866/100/0/threaded
http://www.securityfocus.com/archive/1/442437/100/0/threaded
http://www.redhat.com/support/errata/RHSA-2006-0568.html
http://www.redhat.com/support/errata/RHSA-2006-0567.html
http://www.php.net/release_5_1_3.php
http://www.novell.com/linux/security/advisories/2006_34_php4.html
http://www.novell.com/linux/security/advisories/2006_31_php.html
http://www.mandriva.com/security/advisories?name=MDKSA-2006:122
http://www.hardened-php.net/hphp/zend_hash_del_key_or_index_vulnerability.html
http://www.debian.org/security/2006/dsa-1206
http://support.avaya.com/elmodocs2/security/ASA-2006-175.htm
http://securitytracker.com/id?1016649
http://securitytracker.com/id?1016306
http://secunia.com/advisories/22713
http://secunia.com/advisories/22225
http://secunia.com/advisories/21723
http://secunia.com/advisories/21252
http://secunia.com/advisories/21202
http://secunia.com/advisories/21135
http://secunia.com/advisories/21125
http://secunia.com/advisories/21050
http://secunia.com/advisories/21031
http://secunia.com/advisories/19927
http://rhn.redhat.com/errata/RHSA-2006-0549.html
http://cvs.php.net/viewcvs.cgi/Zend/zend_hash.c?hideattic=0&view=log
http://cvs.php.net/viewcvs.cgi/Zend/zend_hash.c?hideattic=0&r1=1.87.4.8.2.1&r2=1.87.4.8.2.2
http://archives.neohapsis.com/archives/fulldisclosure/2006-08/0166.html