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 object's prototype, causing applications to inherit unintended values when accessing properties without own-property checks.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
High
Complete data modification
Availability
None
No disruption
CVSS Vector v4.0
Weakness Type (CWE)
References 4
https://github.com/TehShrike/deepmerge
disclosure@vulncheck.com
https://github.com/TehShrike/deepmerge/blob/5b87756a5671635679001cbac72aa42f234…
disclosure@vulncheck.com
https://github.com/TehShrike/deepmerge/issues/273
disclosure@vulncheck.com
https://www.vulncheck.com/advisories/deepmerge-through-4.3.1-prototype-poisonin…
disclosure@vulncheck.com