CWE-784 Reliance on Cookies without Validation and Integrity Checking in a Security Decision

The product uses a protection mechanism that relies on the existence or values of a cookie, but it does not properly ensure that the cookie is valid for the associated user.

• Access Control: Bypass Protection Mechanism, Gain Privileges or Assume Identity — It is dangerous to use cookies to set a user's privileges or perform other security-critical actions. Attackers can easily modify cookies, within the browser or by implementing the client-side code outside of the browser. The cookie can be manipulated to claim a high level of authorization, or to claim that successful authentication has occurred.

• [Architecture and Design] Avoid using cookie data for a security-related decision. • [Implementation] Perform thorough input validation (i.e.: server side validation) on the cookie data if you're going to use it for a security related decision. • [Architecture and Design] Add integrity checks to detect tampering. • [Architecture and Design] Protect critical cookies from replay attacks, since cross-site scripting or other attacks may allow attackers to steal a strongly-encrypted cookie that also passes integrity checks. This mitigation applies to cookies that should only be valid during a single transaction or session. By enforcing timeouts, you may limit the scope of an attack. As part of your integrity check, use an unpredictable, server-side value that is not exposed to the client.

• CVE-2009-1549: Attacker can bypass authentication by setting a cookie to a specific value. • CVE-2009-1619: Attacker can bypass authentication and gain admin privileges by setting an "admin" cookie to 1. • CVE-2009-0864: Content management system allows admin privileges by setting a "login" cookie to "OK." • CVE-2008-5784: e-dating application allows admin privileges by setting the admin cookie to 1. • CVE-2008-6291: Web-based email list manager allows attackers to gain admin privileges by setting a login cookie to "admin."