deepmerge through 4.3.1 contains a prototype poisoning vulnerability in the mergeObject() function that fails to properly validate keys being written to target objects. Attackers can supply malicious source objects in merge operations to inject attacker-controlled properties into the returned objects prototype, causing applications to inherit unintended values when accessing properties without own-property checks.
Weakness
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.
Potential Mitigations
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/1.html
- https://cwe.mitre.org/data/definitions/180.html
- https://cwe.mitre.org/data/definitions/77.html
References
- https://github.com/TehShrike/deepmerge
- https://github.com/TehShrike/deepmerge/blob/5b87756a5671635679001cbac72aa42f23472c81/index.js#L39-L60
- https://github.com/TehShrike/deepmerge/issues/273
- https://www.vulncheck.com/advisories/deepmerge-through-4.3.1-prototype-poisoning-via-mergeobject
- https://github.com/TehShrike/deepmerge/issues/273