CVE-2021-213686.7MediumCWE-915

CVE-2021-21368: Prototype poisoning

mcollina · msgpack5

Affected: mcollina msgpack5 · Exploitation: possible (1 to 10%)

Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.

1.6%probability of exploitation in the next 30 days

76th percentile

050100

Higher than 76% of scored CVEs

6.7MediumCVSS 3.1

LowMediumHighCrit.

DescriptionCVE.org

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.

Affected products1

From the CVE record. A product or version that is not listed is unknown, not unaffected.

mcollina · msgpack5< 3.6.1; >= 4.0.0, < 4.5.1; >= 5.0.0, < 5.2.1

On the Atlas

Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.

Open the Atlas

Exploitation: Possible (1 to 10%). EPSS between 1% and 10%.
CISA KEV: Not listed
Public check: No public nuclei template
Weakness: Improperly Controlled Modification of Dynamically-Determined Object Attributes · Deserialization and Object Injection
Vendor: mcollina
Published: March 2021
Band: Possible (1 to 10%), March 2021

CoverageNo articles yet

No CyberSIXT article names CVE-2021-21368 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.