What CVEs are caused by CWE-639?

2,776 recorded CVEs are attributed to CWE-639, including CVE-2026-55255, CVE-2024-34323, CVE-2026-69865. 1 are listed in CISA's Known Exploited Vulnerabilities (KEV) catalog.

What are the consequences of CWE-639?

Exploiting CWE-639 can lead to: Bypass Protection Mechanism, Gain Privileges or Assume Identity.

Is CWE-639 actively exploited?

Yes. 1 CWE-639 vulnerabilities are in CISA's KEV catalog of actively exploited flaws, out of 2,776 recorded CVEs.

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Base weakness

Incomplete

CWE-639: Authorization Bypass Through User-Controlled Key

Also known as: Insecure Direct Object Reference / IDOR, Broken Object Level Authorization / BOLA, Horizontal Authorization

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.

Last updated May 1, 2026

2,776

Recorded CVEs

With this primary weakness

1

KEVs

In the CISA KEV catalog

High

Likelihood of exploit

Per MITRE

Base

Abstraction

MITRE classification

Overview

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.

Real-world CVEs

2,776 recorded CVEs are caused by CWE-639 (Authorization Bypass Through User-Controlled Key), including 1 in CISA's KEV (Known Exploited Vulnerabilities) catalog. KEVs are shown first. 1,696 new CWE-639 CVEs have been recorded so far in 2026 (384 in 2025).

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Common consequences

What can happen when CWE-639 is exploited.

Bypass Protection Mechanism

Affects: Access Control

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

Gain Privileges or Assume Identity

Affects: Access Control

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

Gain Privileges or Assume Identity

Affects: 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.

How it happens

When it is introduced

Typically introduced during these phases of the software lifecycle.

Architecture and Design

How to prevent it

Practical mitigations for CWE-639, grouped by where in the lifecycle they apply.

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.

How to detect it

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

Code examples

MITRE examples of the weakness in code.

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.

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.

Illustrative examples

Real CVEs that MITRE cites as examples of this weakness.

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.

Terminology & mappings

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 appears to have some overlap, but BOLA may be applicable to other weaknesses in addition to this one.
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.

Frequently asked questions

Common questions about CWE-639.

What is CWE-639?: 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.
What CVEs are caused by CWE-639?: 2,776 recorded CVEs are attributed to CWE-639, including CVE-2026-55255, CVE-2024-34323, CVE-2026-69865. 1 are listed in CISA's Known Exploited Vulnerabilities (KEV) catalog.
How do you prevent CWE-639?: For each and every data access, ensure that the user has sufficient privilege to access the record that is being requested.
How is CWE-639 detected?: 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.)
What are the consequences of CWE-639?: Exploiting CWE-639 can lead to: Bypass Protection Mechanism, Gain Privileges or Assume Identity.
Is CWE-639 actively exploited?: Yes. 1 CWE-639 vulnerabilities are in CISA's KEV catalog of actively exploited flaws, out of 2,776 recorded CVEs.

References

Weakness data is sourced from the MITRE CWE catalog (v4.20). CVE associations are aggregated and kept current by RadicalNotion.AI.

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Overview

Real-world CVEs

Common consequences

How it happens

When it is introduced

How to prevent it

How to detect it

Automated Static Analysis

Code examples

Illustrative examples

Related weaknesses

Parent

Child

Terminology & mappings

Alternate terms

Frequently asked questions

References

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