CWE

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

ID: 784		Date: (C)2012-05-14   (M)2022-10-10
Type: weakness		Status: DRAFT
Abstraction Type: Variant

Description

The application 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.

Extended 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.

Likelihood of Exploit: High

Applicable Platforms
Language Class: Language-independent
Architectural Paradigm: Web-based
Architectural Paradigm: Often

Time Of Introduction

• Architecture and Design
• Implementation

Common Consequences

Scope	Technical Impact	Notes
Access_Control	Bypass protection mechanism Gain privileges / 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.

Detection Methods
None

Potential Mitigations

Phase	Strategy	Description	Effectiveness	Notes
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.

Relationships

Related CWE	Type	View	Chain
CWE-784 ChildOf CWE-442	Category	CWE-699

Demonstrative Examples   (Details)

1. In the following example, an authentication flag is read from a browser cookie, thus allowing for external control of user state data. (Demonstrative Example Id DX-17)
2. The following code could be for a medical records application. It performs authentication by checking if a cookie has been set. (Demonstrative Example Id DX-16)
3. The following code excerpt reads a value from a browser cookie to determine the role of the user. (Demonstrative Example Id DX-15)

Observed Examples

1. CVE-2009-1549 : Attacker can bypass authentication by setting a cookie to a specific value.
2. CVE-2009-1619 : Attacker can bypass authentication and gain admin privileges by setting an "admin" cookie to 1.
3. CVE-2009-0864 : Content management system allows admin privileges by setting a "login" cookie to "OK."
4. CVE-2008-5784 : e-dating application allows admin privileges by setting the admin cookie to 1.
5. CVE-2008-6291 : Web-based email list manager allows attackers to gain admin privileges by setting a login cookie to "admin."

For more examples, refer to CVE relations in the bottom box.

White Box Definitions
None

Black Box Definitions
None

Taxynomy Mappings
None

References:

1. Steve Christey .Unforgivable Vulnerabilities. 2007-08-02.
2. M. Howard D. LeBlanc .Writing Secure Code 2nd Edition. Microsoft. Section:'Chapter 13, "Sensitive Data in Cookies and Fields" Page 435'. Published on 2002.