Typical severity: High. Likelihood of attack: Medium. The adversary modifies state information maintained by the target software or causes a state transition in hardware. If successful, the target will use this tainted state and execute in an unintended manner. State management is an important function within a software application. User state maintained by the application can include usernames, payment information, browsing history as well as application-specific contents such as items in a shopping cart. Manipulating user state can be employed by an adversary to elevate privilege, conduct fraudulent transactions or otherwise modify the flow of the application to derive certain benefits. If there is a hardware logic error in a finite state machine, the adversary can use this to put the system in an undefined state which could cause a denial of service or exposure of secure data.
Do not rely solely on user-controllable locations, such as cookies or URL parameters, to maintain user state. | Avoid sensitive information, such as usernames or authentication and authorization information, in user-controllable locations. | Sensitive information that is part of the user state must be appropriately protected to ensure confidentiality and integrity at each request. | All possible states must be handled by hardware finite state machines.