CVE 2010-4697

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.

See the CVE page on Mitre.org for more details.