Like the other PHP bugs, this one is mentioned in 230556, but not explicitly
closed and documented in any errata that I can find.

-------------------------------------------------------------------

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.

    * MISC:http://www.php-security.org/MOPB/MOPB-30-2007.html
    * DEBIAN:DSA-1283
    * URL:http://www.debian.org/security/2007/dsa-1283
    * UBUNTU:USN-455-1
    * URL:http://www.ubuntu.com/usn/usn-455-1
    * BID:23119
    * URL:http://www.securityfocus.com/bid/23119
    * SECUNIA:25062
    * URL:http://secunia.com/advisories/25062