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

Description

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.

Attackers can easily modify cookies, within the browser or by implementing the client-side code outside of the browser. Attackers can bypass protection mechanisms such as authorization and authentication by modifying the cookie to contain an expected value.

Common consequences

• Access Control→Bypass Protection Mechanism,Gain Privileges or Assume Identity
  It is dangerous to use cookies to set a user's privileges. The cookie can be manipulated to claim a high level of authorization, or to claim that successful authentication has occurred.

Potential mitigations

• 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, s

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