CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
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.
- Abstraction
- VariantA weakness tied to a specific language, technology or resource.
- Likelihood of exploit
- Not rated by MITRE
- Status
- Incomplete
Common consequences
- ConfidentialityIntegrityAvailability
Read Application Data; Modify Application Data
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. An attacker can inject attributes that are used in other components by adding or modifying attributes of an object prototype. This creates attributes...
- Availability
DoS: Crash, Exit, or Restart
An attacker can override existing attributes with ones that have incompatible type, which may lead to a crash.
Potential mitigations
- ImplementationEffectiveness: High
By freezing the object prototype first (for example, Object.freeze(Object.prototype)), modification of the prototype becomes impossible.
- Architecture and DesignEffectiveness: High
By blocking modifications of attributes that resolve to object prototype, such as proto or prototype, this weakness can be mitigated.
- ImplementationInput ValidationEffectiveness: Limited
When handling untrusted objects, validating using a schema can be used.
- ImplementationEffectiveness: High
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.
- ImplementationEffectiveness: Moderate
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.