session.c in the session extension in PHP before 5.2.13, and 5.3.1, does not properly interpret ; (semicolon) characters in the argument to the session_save_path function, which allows context-dependent attackers to bypass open_basedir and safe_mode restrictions via an argument that contains multiple ; characters in conjunction with a … (dot dot).
secunia.com/advisories/38708
securityreason.com/achievement_securityalert/82
securityreason.com/securityalert/7008
securitytracker.com/id?1023661
svn.php.net/viewvc/php/php-src/branches/PHP_5_2/ext/session/session.c?r1=293036&r2=294272
svn.php.net/viewvc/php/php-src/branches/PHP_5_2/ext/session/session.c?view=log
svn.php.net/viewvc/php/php-src/branches/PHP_5_3/ext/session/session.c?r1=293036&r2=294272
svn.php.net/viewvc/php/php-src/branches/PHP_5_3/ext/session/session.c?view=log
www.php.net/ChangeLog-5.php
www.php.net/releases/5_2_13.php
www.vupen.com/english/advisories/2010/0479