Simple Machines Forum (SMF) 1.1RCx before 1.1RC3 and 1.0.x before 1.0.8 does not properly unset variables when the input data includes a numeric parameter with a value matching an alphanumeric parameter's hash value which allows remote attackers to perform directory traversal attacks to read arbitrary local files lock topics and possibly have other security impacts. NOTE: it could be argued that this vulnerability is due to a bug in the unset PHP command (CVE-2006-3017) and the proper fix should be in PHP; if so then this should not be treated as a vulnerability in Simple Machines Forum.