Simple Machines Forum (SMF) before 1.1.13, and 2.x before 2.0 RC5, does not properly validate the start parameter, which might allow remote attackers to conduct SQL injection attacks, obtain sensitive information, or cause a denial of service via a crafted value, related to the cleanRequest function in QueryString.php and the constructPageIndex function in Subs.php.
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.