The compress.bzip2:// URL wrapper provided by the bz2 extension in PHP before 4.4.7, and 5.x before 5.2.2, does not implement safemode or open_basedir checks, which allows remote attackers to read bzip2 archives located outside of the intended directories.
http://www.vupen.com/english/advisories/2007/2732
http://www.securityfocus.com/bid/25159
http://www.securityfocus.com/bid/22954
http://www.php-security.org/MOPB/MOPB-21-2007.html
http://www.novell.com/linux/security/advisories/2007_32_php.html
http://us2.php.net/releases/5_2_2.php
http://us2.php.net/releases/4_4_7.php
http://secunia.com/advisories/26235
http://secunia.com/advisories/25056
http://lists.apple.com/archives/security-announce//2007/Jul/msg00004.html