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.

Primary

Implementation

High

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.

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.

The following code excerpt reads a value from a browser cookie to determine the role of the user.

Cookie[] cookies = request.getCookies();for (int i =0; i< cookies.length; i++) {Cookie c = cookies[i];if (c.getName().equals("role")) {userRole = c.getValue();}}

The following code could be for a medical records application. It performs authentication by checking if a cookie has been set.

$auth = $_COOKIES['authenticated'];if (! $auth) {if (AuthenticateUser($_POST['user'], $_POST['password']) == "success") {// save the cookie to send out in future responsessetcookie("authenticated", "1", time()+60*60*2);}else {ShowLoginScreen();die("\n");}}DisplayMedicalHistory($_POST['patient_ID']);

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.

Cookie[] cookies = request.getCookies();for (int i =0; i< cookies.length; i++) {Cookie c = cookies[i];if (c.getName().equals("authenticated") && Boolean.TRUE.equals(c.getValue())) {authenticated = true;}}

CVE-2009-1549
Attacker can bypass authentication by setting a cookie to a specific value.
https://www.cve.org/CVERecord?id=CVE-2009-1549

CVE-2009-1619
Attacker can bypass authentication and gain admin privileges by setting an "admin" cookie to 1.
https://www.cve.org/CVERecord?id=CVE-2009-1619

CVE-2009-0864
Content management system allows admin privileges by setting a "login" cookie to "OK."
https://www.cve.org/CVERecord?id=CVE-2009-0864

CVE-2008-5784
e-dating application allows admin privileges by setting the admin cookie to 1.
https://www.cve.org/CVERecord?id=CVE-2008-5784

CVE-2008-6291
Web-based email list manager allows attackers to gain admin privileges by setting a login cookie to "admin."
https://www.cve.org/CVERecord?id=CVE-2008-6291

Allowed
This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

A new parent might need to be defined for this entry. This entry is specific to cookies, which reflects the significant number of vulnerabilities being reported for cookie-based authentication in CVE during 2008 and 2009. However, other types of inputs - such as parameters or headers - could also be used for similar authentication or authorization. Similar issues (under the Research view) include CWE-247 and CWE-472.

CWE Content Team
MITRE
2009-07-16
1.5
2009-07-27

CWE Content Team
MITRE
2009-10-29
updated Relationships

CWE Content Team
MITRE
2010-02-16
updated Demonstrative_Examples, References, Relationships

CWE Content Team
MITRE
2011-06-01
updated Common_Consequences

CWE Content Team
MITRE
2017-01-19
updated Relationships

CWE Content Team
MITRE
2017-11-08
updated Modes_of_Introduction, References, Relationships

CWE Content Team
MITRE
2018-03-27
updated References

CWE Content Team
MITRE
2020-02-24
updated Applicable_Platforms, Relationships

CWE Content Team
MITRE
2021-10-28
updated Relationships

CWE Content Team
MITRE
2023-01-31
updated Description

CWE Content Team
MITRE
2023-04-27
updated Modes_of_Introduction, Relationships, Time_of_Introduction

CWE Content Team
MITRE
2023-06-29
updated Mapping_Notes

CWE Content Team
MITRE
2025-12-11
4.19
2025-12-11
updated Applicable_Platforms, Relationships, Weakness_Ordinalities