CWE - CWE-639: Authorization Bypass Through User-Controlled Key (4.18)

Home > CWE List > CWE-639: Authorization Bypass Through User-Controlled Key (4.18)

CWE Glossary Definition

CWE-639: Authorization Bypass Through User-Controlled Key

Weakness ID: 639

Vulnerability Mapping: ALLOWED This CWE ID may be used to map to real-world vulnerabilities
Abstraction: Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.

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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 / IDOR

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.

Broken Object Level Authorization / BOLA

BOLA is used in the 2019 OWASP API Security Top 10 and is said to be the same as IDOR.

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.

Common Consequences

Section HelpThis table 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.

Impact	Details
Bypass Protection Mechanism	Scope: Access Control Access control checks for specific user data or functionality can be bypassed.
Gain Privileges or Assume Identity	Scope: Access Control Horizontal escalation of privilege is possible (one user can view/modify information of another user).
Gain Privileges or Assume Identity	Scope: Access Control 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.

Potential Mitigations

Phase(s)	Mitigation
Architecture and Design	For each and every data access, ensure that the user has sufficient privilege to access the record that is being requested.
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.
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.

Relationships

Section Help This table 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" (View-1000)

Nature	Type	ID	Name
ChildOf	Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	863	Incorrect Authorization
ParentOf	Variant Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource.	566	Authorization Bypass Through User-Controlled SQL Primary Key

Relevant to the view "Software Development" (View-699)

Nature	Type	ID	Name
MemberOf	Category Category - a CWE entry that contains a set of other entries that share a common characteristic.	840	Business Logic Errors
MemberOf	Category Category - a CWE entry that contains a set of other entries that share a common characteristic.	1212	Authorization Errors

Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (View-1003)

Nature	Type	ID	Name
ChildOf	Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.	863	Incorrect Authorization

Relevant to the view "Architectural Concepts" (View-1008)

Nature	Type	ID	Name
MemberOf	Category Category - a CWE entry that contains a set of other entries that share a common characteristic.	1011	Authorize Actors

Relevant to the view "CISQ Data Protection Measures" (View-1340)

Nature	Type	ID	Name
ChildOf	Pillar Pillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. A Pillar is different from a Category as a Pillar is still technically a type of weakness that describes a mistake, while a Category represents a common characteristic used to group related things.	284	Improper Access Control

Modes Of Introduction

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

Phase	Note
Architecture and Design	REALIZATION: This weakness is caused during implementation of an architectural security tactic.

Applicable Platforms

Section HelpThis listing shows 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.

Languages

Class: Not Language-Specific (Undetermined Prevalence)

Likelihood Of Exploit

High

Demonstrative Examples

Example 1

The following code uses a parameterized statement, which escapes metacharacters and prevents SQL injection vulnerabilities, to construct and execute a SQL query that searches for an invoice matching the specified identifier [1]. The identifier is selected from a list of all invoices associated with the current authenticated user.

(bad code)

Example Language: C#

...
conn = new SqlConnection(_ConnectionString);
conn.Open();
int16 id = System.Convert.ToInt16(invoiceID.Text);
SqlCommand query = new SqlCommand( "SELECT * FROM invoices WHERE id = @id", conn);
query.Parameters.AddWithValue("@id", id);
SqlDataReader objReader = objCommand.ExecuteReader();
...

The problem is that the developer has not considered all of the possible values of id. Although the interface generates a list of invoice identifiers that belong to the current user, an attacker can bypass this interface to request any desired invoice. Because the code in this example does not check to ensure that the user has permission to access the requested invoice, it will display any invoice, even if it does not belong to the current user.

Selected Observed Examples

Note: this is a curated list of examples for users to understand the variety of ways in which this weakness can be introduced. It is not a complete list of all CVEs that are related to this CWE entry.

Reference	Description
CVE-2021-36539	An educational application does not appropriately restrict file IDs to a particular user. The attacker can brute-force guess IDs, indicating IDOR.

Detection Methods

Method	Details
Automated Static Analysis	Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.) Effectiveness: High

Method

Details

Automated Static Analysis

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)

Effectiveness: High

Memberships

Section HelpThis 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.

Nature	Type	ID	Name
MemberOf	CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.	715	OWASP Top Ten 2007 Category A4 - Insecure Direct Object Reference
MemberOf	CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.	723	OWASP Top Ten 2004 Category A2 - Broken Access Control
MemberOf	CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.	813	OWASP Top Ten 2010 Category A4 - Insecure Direct Object References
MemberOf	CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.	932	OWASP Top Ten 2013 Category A4 - Insecure Direct Object References
MemberOf	CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.	945	SFP Secondary Cluster: Insecure Resource Access
MemberOf	CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.	1031	OWASP Top Ten 2017 Category A5 - Broken Access Control
MemberOf	CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.	1345	OWASP Top Ten 2021 Category A01:2021 - Broken Access Control
MemberOf	CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.	1396	Comprehensive Categorization: Access Control

Vulnerability Mapping Notes

Usage ALLOWED

(this CWE ID may be used to map to real-world vulnerabilities)

Reason Acceptable-Use

Rationale

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Comments

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.

Content History

Submissions
Submission Date	Submitter	Organization
2008年01月30日 (CWE Draft 8, 2008年01月30日)	Evgeny Lebanidze	Cigital
2008年01月30日 (CWE Draft 8, 2008年01月30日)
Modifications
Modification Date	Modifier	Organization
2024年02月29日 (CWE 4.14, 2024年02月29日)	CWE Content Team	MITRE
2024年02月29日 (CWE 4.14, 2024年02月29日)	updated Demonstrative_Examples
2023年10月26日	CWE Content Team	MITRE
2023年10月26日	updated Observed_Examples
2023年06月29日	CWE Content Team	MITRE
2023年06月29日	updated Mapping_Notes
2023年04月27日	CWE Content Team	MITRE
2023年04月27日	updated Detection_Factors, Relationships
2021年10月28日	CWE Content Team	MITRE
2021年10月28日	updated Relationships
2021年03月15日	CWE Content Team	MITRE
2021年03月15日	updated Alternate_Terms
2020年12月10日	CWE Content Team	MITRE
2020年12月10日	updated Relationships
2020年06月25日	CWE Content Team	MITRE
2020年06月25日	updated Alternate_Terms
2020年02月24日	CWE Content Team	MITRE
2020年02月24日	updated Relationships
2019年06月20日	CWE Content Team	MITRE
2019年06月20日	updated Relationships
2018年03月27日	CWE Content Team	MITRE
2018年03月27日	updated Relationships
2017年11月08日	CWE Content Team	MITRE
2017年11月08日	updated Description, Enabling_Factors_for_Exploitation, Modes_of_Introduction, Relationships
2014年07月30日	CWE Content Team	MITRE
2014年07月30日	updated Relationships
2013年07月17日	CWE Content Team	MITRE
2013年07月17日	updated Relationships
2013年02月21日	CWE Content Team	MITRE
2013年02月21日	updated Alternate_Terms, Common_Consequences
2012年05月11日	CWE Content Team	MITRE
2012年05月11日	updated Relationships
2011年06月01日	CWE Content Team	MITRE
2011年06月01日	updated Common_Consequences, Relationships
2011年03月29日	CWE Content Team	MITRE
2011年03月29日	updated Alternate_Terms, Applicable_Platforms, Description, Name, Potential_Mitigations, Relationships
2010年06月21日	CWE Content Team	MITRE
2010年06月21日	updated Relationships
2009年10月29日	CWE Content Team	MITRE
2009年10月29日	updated Common_Consequences
2009年05月27日	CWE Content Team	MITRE
2009年05月27日	updated Relationships
2009年03月10日	CWE Content Team	MITRE
2009年03月10日	updated Relationships
2008年10月14日	CWE Content Team	MITRE
2008年10月14日	updated Description
2008年09月08日	CWE Content Team	MITRE
2008年09月08日	updated Common_Consequences, Relationships, Type
Previous Entry Names
Change Date	Previous Entry Name
2011年03月29日	Access Control Bypass Through User-Controlled Key

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Page Last Updated: September 09, 2025

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