The session extension in PHP 4 before 4.4.5, and PHP 5 before 5.2.1, calculates the reference count for the session variables without considering the internal pointer from the session globals, which allows context-dependent attackers to execute arbitrary code via a crafted string in the session_register after unsetting HTTP_SESSION_VARS and _SESSION, which destroys the session data Hashtable.
AV:N/AC:L/Au:N/C:P/I:P/A:P
This vulnerability has a 9.02% probability of being exploited in the next 30 days, ranking higher than 95% of all scored CVEs.