Use-after-free vulnerability in the Zend engine in PHP before 5.2.15 and 5.3.x before 5.3.4 might allow context-dependent attackers to cause a denial of service (heap memory corruption) or have unspecified other impact via vectors related to use of __set, __get, __isset, and __unset methods on objects accessed by a reference.
http://marc.info/?l=bugtraq&m=133469208622507&w=2
http://www.php.net/ChangeLog-5.php
http://www.securityfocus.com/bid/45952
https://exchange.xforce.ibmcloud.com/vulnerabilities/65310
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A12528