CWE-1321

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

Medium

Description

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.

Potential Impact

How to Fix

Implementation

By freezing the object prototype first (for example, Object.freeze(Object.prototype)), modification of the prototype becomes impossible.

Architecture and Design

By blocking modifications of attributes that resolve to object prototype, such as proto or prototype, this weakness can be mitigated.

Implementation

When handling untrusted objects, validating using a schema can be used.

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.

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.

Detection Methods

Related Weaknesses

References

View on MITRE CWE Database →

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