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.
