The file upload feature in Drupal 6.x before 6.27 and 7.x before 7.18 allows remote authenticated users to bypass the protection mechanism and execute arbitrary PHP code via a null byte in a file name.
https://exchange.xforce.ibmcloud.com/vulnerabilities/80795
http://www.securityfocus.com/bid/56993
http://www.openwall.com/lists/oss-security/2012/12/20/1