An attacker creates a false but functional session credential in order to gain or usurp access to a service. Session credentials allow users to identify themselves to a service after an initial authentication without needing to resend the authentication information (usually a username and password) with every message. If an attacker is able to forge valid session credentials they may be able to bypass authentication or piggy-back off some other authenticated user's session. This attack differs from Reuse of Session IDs and Session Sidejacking attacks in that in the latter attacks an attacker uses a previous or existing credential without modification while, in a forging attack, the attacker must create their own credential, although it may be based on previously observed credentials.

Not present

1. The targeted application must use session credentials to identify legitimate users. Session identifiers that remains unchanged when the privilege levels change. Predictable session identifiers.

1. Attackers may require tools to craft messages containing their forged credentials, and ability to send HTTP request to a web application.

1. This example uses client side scripting to set session ID in the victim's browser. The JavaScript code document.cookie="sessionid=0123456789" fixates a falsified session credential into victim's browser, with the help of crafted a URL link. http://www.example.com/ A similar example uses session ID as an argument of the URL. http://www.example.com/index.php/sessionid=0123456789 Once the victim clicks the links, the attacker may be able to bypass authentication or piggy-back off some other authenticated victim's session.