Weakness · Medium
CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
What it is
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.
- Severity (our rating)
- Medium
- Likelihood of exploit
- Not rated by MITRE
- Introduced during
- Architecture and Design, Implementation
- Exploited in the wild
- 1 known exploited CVE
What an attacker can do
- Read Application Data (Confidentiality, Integrity, Availability)
- Modify Application Data (Confidentiality, Integrity, Availability)
- DoS: Crash, Exit, or Restart (Availability)
How to prevent it
Implementation
- By freezing the object prototype first (for example, Object.freeze(Object.prototype)), modification of the prototype becomes impossible.
- When handling untrusted objects, validating using a schema can be used.
- 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.
- 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.
Architecture and Design
- By blocking modifications of attributes that resolve to object prototype, such as proto or prototype, this weakness can be mitigated.
How to find 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.)
Exploited in the wild: 1 CVE
Vulnerabilities caused by CWE-1321 that attackers have used, from CISA's Known Exploited Vulnerabilities catalog, newest first.
H2 Security
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Start freeSource: MITRE Common Weakness Enumeration, CWE version 4.19.1. CWE is a trademark of The MITRE Corporation.