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.

We track 3 vulnerabilities of this type. 100% are rated high or critical, and the average CVSS score is 8.5.

How this weakness is prevented

• 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.