PHP 5 before 5.2.7 does not enforce the error_log safe_mode restrictions when safe_mode is enabled through a php_admin_flag setting in httpd.conf, which allows context-dependent attackers to write to arbitrary files by placing a "php_value error_log" entry in a .htaccess file.
https://www.exploit-db.com/exploits/7171
https://exchange.xforce.ibmcloud.com/vulnerabilities/47314
http://www.securityfocus.com/bid/32383
http://www.securityfocus.com/archive/1/501376/100/0/threaded
http://www.php.net/ChangeLog-5.php#5.2.7
http://www.mandriva.com/security/advisories?name=MDVSA-2009:045
http://wiki.rpath.com/Advisories:rPSA-2009-0035
http://secunia.com/advisories/35650
http://marc.info/?l=bugtraq&m=125631037611762&w=2
http://marc.info/?l=bugtraq&m=124654546101607&w=2
http://archives.neohapsis.com/archives/bugtraq/2008-11/0152.html