#VU76823 Prototype pollution in msgpack5 - CVE-2021-21368

Vulnerability identifier: #VU76823

Vulnerability risk: Medium

CVSSv4.0: 6.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-21368

CWE-ID: CWE-1321

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
msgpack5
Other software / Other software solutions

Vendor: mcollina

Description

The vulnerability allows a remote user to execute arbitrary JavaScript code.

The vulnerability occrures 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. A remote user can pass specially crafted input to the application and perform prototype pollution, which can result in information disclosure or data manipulation.

Mitigation
Cybersecurity Help is currently unaware of any official solution to address this vulnerability..

Vulnerable software versions

msgpack5: 3.0.0 - 5.2.0

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External links
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

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.