CVE-2021-21368 Information

Description

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 Vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Reference

https://github.com/mcollina/msgpack5/releases/tag/v3.6.1 https://github.com/mcollina/msgpack5/releases/tag/v5.2.1 https://github.com/mcollina/msgpack5/releases/tag/v4.5.1 https://github.com/mcollina/msgpack5/commit/d4e6cb956ae51c8bb2828e71c7c1107c340cf1e8 https://github.com/mcollina/msgpack5/security/advisories/GHSA-gmjw-49p4-pcfm https://www.npmjs.com/package/msgpack5

Attack Complexity

LOW

Privileges Required

LOW

User Interaction Required

LOW

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

HIGH

Availability Impact

HIGH

Base Score

HIGH

Base Severity

8.8