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CWE-639: Authorization Bypass Through User-Controlled Key

Weakness ID: 639
Abstraction: Base
Structure: Simple
Status: Incomplete
Presentation Filter:
+ Description
The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.
+ Extended Description

Retrieval of a user record occurs in the system based on some key value that is under user control. The key would typically identify a user-related record stored in the system and would be used to lookup that record for presentation to the user. It is likely that an attacker would have to be an authenticated user in the system. However, the authorization process would not properly check the data access operation to ensure that the authenticated user performing the operation has sufficient entitlements to perform the requested data access, hence bypassing any other authorization checks present in the system.

For example, attackers can look at places where user specific data is retrieved (e.g. search screens) and determine whether the key for the item being looked up is controllable externally. The key may be a hidden field in the HTML form field, might be passed as a URL parameter or as an unencrypted cookie variable, then in each of these cases it will be possible to tamper with the key value.

One manifestation of this weakness is when a system uses sequential or otherwise easily-guessable session IDs that would allow one user to easily switch to another user's session and read/modify their data.

+ Alternate Terms
Insecure Direct Object Reference:
The "Insecure Direct Object Reference" term, as described in the OWASP Top Ten, is broader than this CWE because it also covers path traversal (CWE-22). Within the context of vulnerability theory, there is a similarity between the OWASP concept and CWE-706: Use of Incorrectly-Resolved Name or Reference.
Horizontal Authorization:
"Horizontal Authorization" is used to describe situations in which two users have the same privilege level, but must be prevented from accessing each other's resources. This is fairly common when using key-based access to resources in a multi-user context.
+ Relationships

The table(s) below shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.

+ Relevant to the view "Research Concepts" (CWE-1000)
+ Relevant to the view "Architectural Concepts" (CWE-1008)
MemberOfCategoryCategory1011Authorize Actors
+ Relevant to the view "Development Concepts" (CWE-699)
MemberOfCategoryCategory840Business Logic Errors
ChildOfClassClass862Missing Authorization
ParentOfVariantVariant566Authorization Bypass Through User-Controlled SQL Primary Key
+ Modes Of Introduction

The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the software life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.

Architecture and DesignREALIZATION: This weakness is caused during implementation of an architectural security tactic.
+ Applicable Platforms
The listings below show possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.


Class: Language-Independent (Undetermined Prevalence)

+ Common Consequences

The table below specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.

Access Control

Technical Impact: Bypass Protection Mechanism

Access control checks for specific user data or functionality can be bypassed.
Access Control

Technical Impact: Gain Privileges or Assume Identity

Horizontal escalation of privilege is possible (one user can view/modify information of another user).
Access Control

Technical Impact: Gain Privileges or Assume Identity

Vertical escalation of privilege is possible if the user-controlled key is actually a flag that indicates administrator status, allowing the attacker to gain administrative access.
+ Likelihood Of Exploit
+ Potential Mitigations

Phase: Architecture and Design

For each and every data access, ensure that the user has sufficient privilege to access the record that is being requested.

Phases: Architecture and Design; Implementation

Make sure that the key that is used in the lookup of a specific user's record is not controllable externally by the user or that any tampering can be detected.

Phase: Architecture and Design

Use encryption in order to make it more difficult to guess other legitimate values of the key or associate a digital signature with the key so that the server can verify that there has been no tampering.
+ Memberships
This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
+ Content History
Submission DateSubmitterOrganization
2008-01-30Evgeny LebanidzeCigital
Modification DateModifierOrganization
2008-09-08CWE Content TeamMITRE
updated Common_Consequences, Relationships, Type
2008-10-14CWE Content TeamMITRE
updated Description
2009-03-10CWE Content TeamMITRE
updated Relationships
2009-05-27CWE Content TeamMITRE
updated Relationships
2009-10-29CWE Content TeamMITRE
updated Common_Consequences
2010-06-21CWE Content TeamMITRE
updated Relationships
2011-03-29CWE Content TeamMITRE
updated Alternate_Terms, Applicable_Platforms, Description, Name, Potential_Mitigations, Relationships
2011-06-01CWE Content TeamMITRE
updated Common_Consequences, Relationships
2012-05-11CWE Content TeamMITRE
updated Relationships
2013-02-21CWE Content TeamMITRE
updated Alternate_Terms, Common_Consequences
2013-07-17CWE Content TeamMITRE
updated Relationships
2014-07-30CWE Content TeamMITRE
updated Relationships
2017-11-08CWE Content TeamMITRE
updated Description, Enabling_Factors_for_Exploitation, Modes_of_Introduction, Relationships
Previous Entry Names
Change DatePrevious Entry Name
2011-03-29Access Control Bypass Through User-Controlled Key

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Page Last Updated: January 18, 2018