CWE-784: Reliance on Cookies without Validation and Integrity Checking in a Security Decision
Official CWE-784 CWE context with Glexia analysis, remediation guidance, related CVEs, and ATT&CK context.
Glexia's Take
CWE-784: Reliance on Cookies without Validation and Integrity Checking in a Security Decision
Reliance on Cookies without Validation and Integrity Checking in a Security Decision represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Executive Impact
- 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.
Developer Pattern
CWE-784 is the kind of defect developers can usually prevent with explicit validation, safer framework defaults, and tests that exercise hostile input or unsafe state transitions.
Confidence
high confidence from CWE-784, 4.20.
Official CWE Definition
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.
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.
Developer And Remediation Guidance
How teams prevent and detect this weakness
Causes
- The following code excerpt reads a value from a browser cookie to determine the role of the user.
- The following code could be for a medical records application. It performs authentication by checking if a cookie has been set. The programmer expects that the AuthenticateUser() check will always be applied, and the "authenticated" cookie will only be set when authentication succeeds. The programmer even diligently specifies a 2-hour expiration for the cookie.,However, the attacker can set the "authenticated" cookie to a non-zero value such as 1. As a result, the $auth variable is 1, and the AuthenticateUser() check is not even performed. The attacker has bypassed the authentication.
- In the following example, an authentication flag is read from a browser cookie, thus allowing for external control of user state data.
Remediation
- 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.
Detection
- Code review
- SAST
- DAST
- Focused regression tests
Mappings
Related CVEs, CWEs, and ATT&CK context
Related CWEs
ATT&CK Relevance
ATT&CK relevance is shown only when reviewed or responsibly inferred.