The session extension in PHP before 5.2.4 might allow local users to bypass open_basedir restrictions via a session file that is a symlink.
https://issues.rpath.com/browse/RPL-1702
https://issues.rpath.com/browse/RPL-1693
https://exchange.xforce.ibmcloud.com/vulnerabilities/36387
http://www.vupen.com/english/advisories/2007/3023
http://www.trustix.org/errata/2007/0026/
http://www.php.net/releases/5_2_4.php
http://www.php.net/ChangeLog-5.php#5.2.4
http://www.gentoo.org/security/en/glsa/glsa-200710-02.xml
http://secunia.com/advisories/27377
http://secunia.com/advisories/27102
http://secunia.com/advisories/26838