CWE-1321 Detail

CWE-1321

Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Incomplete
2020-12-10
00h00 +00:00
2024-02-29
00h00 +00:00
CWE Mitre.org
Notifications for a CWE
Stay informed of any changes for a specific CWE.
Notifications manage

Name: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype.

CWE Description

By adding or modifying attributes of an object prototype, it is possible to create attributes that exist on every object, or replace critical attributes with malicious ones. This can be problematic if the product depends on existence or non-existence of certain attributes, or uses pre-defined attributes of object prototype (such as hasOwnProperty, toString or valueOf).

This weakness is usually exploited by using a special attribute of objects called proto, constructor or prototype. Such attributes give access to the object prototype. This weakness is often found in code that assigns object attributes based on user input, or merges or clones objects recursively.

General Informations

Modes Of Introduction

Architecture and Design
Implementation

Applicable Platforms

Language

Name: JavaScript (Undetermined)

Common Consequences

Scope Impact Likelihood
IntegrityModify Application Data

Note: An attacker can inject attributes that are used in other components.		High
AvailabilityDoS: Crash, Exit, or Restart

Note: An attacker can override existing attributes with ones that have incompatible type, which may lead to a crash.		High

Observed Examples

References Description

CVE-2018-3721

Prototype pollution by merging objects.

CVE-2019-10744

Prototype pollution by setting default values to object attributes recursively.

CVE-2019-11358

Prototype pollution by merging objects recursively.

CVE-2020-8203

Prototype pollution by setting object attributes based on dot-separated path.

Potential Mitigations

Phases : Implementation
By freezing the object prototype first (for example, Object.freeze(Object.prototype)), modification of the prototype becomes impossible.
Phases : Architecture and Design
By blocking modifications of attributes that resolve to object prototype, such as proto or prototype, this weakness can be mitigated.
Phases : Implementation
When handling untrusted objects, validating using a schema can be used.
Phases : Implementation
By using an object without prototypes (via Object.create(null) ), adding object prototype attributes by accessing the prototype via the special attributes becomes impossible, mitigating this weakness.
Phases : Implementation
Map can be used instead of objects in most cases. If Map methods are used instead of object attributes, it is not possible to access the object prototype or modify it.

Vulnerability Mapping Notes

Justification : 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.
Comment : 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.

Related Attack Patterns

CAPEC-ID Attack Pattern Name
CAPEC-1 Accessing Functionality Not Properly Constrained by ACLs
In applications, particularly web applications, access to functionality is mitigated by an authorization framework. This framework maps Access Control Lists (ACLs) to elements of the application's functionality; particularly URL's for web apps. In the case that the administrator failed to specify an ACL for a particular element, an attacker may be able to access it with impunity. An attacker with the ability to access functionality not properly constrained by ACLs can obtain sensitive information and possibly compromise the entire application. Such an attacker can access resources that must be available only to users at a higher privilege level, can access management sections of the application, or can run queries for data that they otherwise not supposed to.
CAPEC-180 Exploiting Incorrectly Configured Access Control Security Levels
An attacker exploits a weakness in the configuration of access controls and is able to bypass the intended protection that these measures guard against and thereby obtain unauthorized access to the system or network. Sensitive functionality should always be protected with access controls. However configuring all but the most trivial access control systems can be very complicated and there are many opportunities for mistakes. If an attacker can learn of incorrectly configured access security settings, they may be able to exploit this in an attack.
CAPEC-77 Manipulating User-Controlled Variables
This attack targets user controlled variables (DEBUG=1, PHP Globals, and So Forth). An adversary can override variables leveraging user-supplied, untrusted query variables directly used on the application server without any data sanitization. In extreme cases, the adversary can change variables controlling the business logic of the application. For instance, in languages like PHP, a number of poorly set default configurations may allow the user to override variables.

References

REF-1148

Prototype pollution attack in NodeJS application
Olivier Arteau.
https://github.com/HoLyVieR/prototype-pollution-nsec18/blob/master/paper/JavaScript_prototype_pollution_attack_in_NodeJS.pdf

REF-1149

What is Prototype Pollution?
Changhui Xu.
https://codeburst.io/what-is-prototype-pollution-49482fc4b638

Submission

Name Organization Date Date release Version
Anonymous External Contributor 2020-08-25 +00:00 2020-12-10 +00:00 4.3

Modifications

Name Organization Date Comment
CWE Content Team MITRE 2021-10-28 +00:00 updated Relationships
CWE Content Team MITRE 2023-01-31 +00:00 updated Description
CWE Content Team MITRE 2023-04-27 +00:00 updated Relationships
CWE Content Team MITRE 2023-06-29 +00:00 updated Mapping_Notes
CWE Content Team MITRE 2024-02-29 +00:00 updated Demonstrative_Examples