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.
View on MITREExtended Description
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.
Technical Details
- Structure
- Simple
Applicable To
Security Consequences
Scope
Impact
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.
Mitigation Strategies
Phase
Description
Avoid using cookie data for a security-related decision.
Phase
Description
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.
Phase
Description
Add integrity checks to detect tampering.
Phase
Description
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 Methods
No detection method information available for this CWE.
Code Examples & CVEs
Demonstrative Examples
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.
In the following example, an authentication flag is read from a browser cookie, thus allowing for external control of user state data.
Observed CVE Examples (5)
Attacker can bypass authentication by setting a cookie to a specific value.
View DetailsAttacker can bypass authentication and gain admin privileges by setting an "admin" cookie to 1.
View DetailsContent management system allows admin privileges by setting a "login" cookie to "OK."
View Detailse-dating application allows admin privileges by setting the admin cookie to 1.
View DetailsWeb-based email list manager allows attackers to gain admin privileges by setting a login cookie to "admin."
View DetailsCWE Relationships
Frequently Asked Questions
What is CWE-784: Reliance on Cookies without Validation and Integrity Checking in a Security Decision?+
CWE-784: Reliance on Cookies without Validation and Integrity Checking in a Security Decision is a Common Weakness Enumeration (CWE) entry maintained by MITRE. 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.
What are the security consequences of Reliance on Cookies without Validation and Integrity Checking in a Security Decision?+
If exploited, CWE-784 (Reliance on Cookies without Validation and Integrity Checking in a Security Decision) it can compromise Access Control, leading to outcomes such as Bypass Protection Mechanism and Gain Privileges or Assume Identity.
How do you prevent or mitigate Reliance on Cookies without Validation and Integrity Checking in a Security Decision?+
Recommended mitigations for CWE-784 include: Avoid using cookie data for a security-related decision. 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. Add integrity checks to detect tampering.
Which programming languages are affected by Reliance on Cookies without Validation and Integrity Checking in a Security Decision?+
CWE-784 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.
What are real-world examples of Reliance on Cookies without Validation and Integrity Checking in a Security Decision?+
MITRE documents real CVEs mapped to CWE-784, including CVE-2009-1549, CVE-2009-1619, CVE-2009-0864, CVE-2008-5784 and CVE-2008-6291. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.
What is the difference between a CWE and a CVE?+
A CWE (Common Weakness Enumeration) like CWE-784 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.