When server side functionality relies on file name and/or file extension of a user supplied file to determine the proper course of action, such as selecting the correct process to which control should be passed, deciding what data should be made available or what resources should be allocated, it becomes possible for an attacker to deliberately cause the server side code to misclassify the supplied file in order to gain some advantage. It might become possible for an attacker to cause exhaustion of resources, denial of service, information disclosure of debug or system data (including application source code), or being bound to a particular server side process. This weakness may be due to a vulnerability in any of the technologies used by the web and application servers, due to misconfiguration or to a flaw in the application itself.