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NOTICE UPDATED - April, 25th 2024

NIST has updated the NVD program announcement page with additional information regarding recent concerns and the temporary delays in enrichment efforts.

CVE-2021-21368 Detail


msgpack5 is a msgpack v5 implementation for node.js and the browser. In msgpack5 before versions 3.6.1, 4.5.1, and 5.2.1 there is a "Prototype Poisoning" vulnerability. When msgpack5 decodes a map containing a key "__proto__", it assigns the decoded value to __proto__. Object.prototype.__proto__ is an accessor property for the receiver's prototype. If the value corresponding to the key __proto__ decodes to an object or null, msgpack5 sets the decoded object's prototype to that value. An attacker who can submit crafted MessagePack data to a service can use this to produce values that appear to be of other types; may have unexpected prototype properties and methods (for example length, numeric properties, and push et al if __proto__'s value decodes to an Array); and/or may throw unexpected exceptions when used (for example if the __proto__ value decodes to a Map or Date). Other unexpected behavior might be produced for other types. There is no effect on the global prototype. This "prototype poisoning" is sort of a very limited inversion of a prototype pollution attack. Only the decoded value's prototype is affected, and it can only be set to msgpack5 values (though if the victim makes use of custom codecs, anything could be a msgpack5 value). We have not found a way to escalate this to true prototype pollution (absent other bugs in the consumer's code). This has been fixed in msgpack5 version 3.6.1, 4.5.1, and 5.2.1. See the referenced GitHub Security Advisory for an example and more details.


CVSS 4.0 Severity and Metrics:

NVD assessment not yet provided.

NVD Analysts use publicly available information to associate vector strings and CVSS scores. We also display any CVSS information provided within the CVE List from the CNA.

Note: NVD Analysts have not published a CVSS score for this CVE at this time. NVD Analysts use publicly available information at the time of analysis to associate CVSS vector strings.

References to Advisories, Solutions, and Tools

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Hyperlink Resource
https://github.com/mcollina/msgpack5/commit/d4e6cb956ae51c8bb2828e71c7c1107c340cf1e8 Patch  Third Party Advisory 
https://github.com/mcollina/msgpack5/releases/tag/v3.6.1 Release Notes  Third Party Advisory 
https://github.com/mcollina/msgpack5/releases/tag/v4.5.1 Release Notes  Third Party Advisory 
https://github.com/mcollina/msgpack5/releases/tag/v5.2.1 Release Notes  Third Party Advisory 
https://github.com/mcollina/msgpack5/security/advisories/GHSA-gmjw-49p4-pcfm Exploit  Third Party Advisory 
https://www.npmjs.com/package/msgpack5 Product  Third Party Advisory 

Weakness Enumeration

CWE-ID CWE Name Source
CWE-1321 Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') cwe source acceptance level NIST  
CWE-915 Improperly Controlled Modification of Dynamically-Determined Object Attributes Contributor acceptance level GitHub, Inc.  

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Change History

4 change records found show changes

Quick Info

CVE Dictionary Entry:
NVD Published Date:
NVD Last Modified:
GitHub, Inc.