DISPUTED QueryString.php in Simple Machines Forum (SMF) 1.0.7 and earlier, and 1.1rc2 and earlier, allows remote attackers to more easily spoof the IP address and evade banning via a modified X-Forwarded-For HTTP header, which is preferred instead of other more reliable sources for the IP address. NOTE: the original researcher claims that the vendor has disputed this issue.

Cross-site scripting (XSS) vulnerability in index.php in Simple Machines Forum (SMF) allows remote attackers to inject arbitrary web script or HTML via a base64 encoded params value in the action parameter.

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.