PHP 5 before 5.2.3 does not enforce the open_basedir or safe_mode restriction in certain cases, which allows context-dependent attackers to determine the existence of arbitrary files by checking if the readfile function returns a string. NOTE: this issue might also involve the realpath function.
https://www.redhat.com/archives/fedora-package-announce/2007-September/msg00397.html
http://www.securityfocus.com/bid/24259
http://www.php.net/releases/5_2_3.php
http://www.gentoo.org/security/en/glsa/glsa-200710-02.xml
http://secunia.com/advisories/27110
http://secunia.com/advisories/27102
http://secunia.com/advisories/26231
http://secunia.com/advisories/26048
http://secunia.com/advisories/25456
http://lists.opensuse.org/opensuse-security-announce/2007-07/msg00006.html