CVE-2026-93753
deepmerge through 4.3.1 Prototype Poisoning via mergeObject
CVSS Score
7.5
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-1321 |
| Vendor | tehshrike |
| Product | deepmerge |
| Published | Sep 18, 2026 |
| Last Updated | Sep 18, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None
Affected Versions
TehShrike / deepmerge
0 ≤ 4.3.1
References
github.com: https://github.com/TehShrike/deepmerge/issues/273 github.com: https://github.com/TehShrike/deepmerge github.com: https://github.com/TehShrike/deepmerge/blob/5b87756a5671635679001cbac72aa42f23472c81/index.js#L39-L60 vulncheck.com: https://www.vulncheck.com/advisories/deepmerge-through-4.3.1-prototype-poisoning-via-mergeobject
Credits
🔍 Wayde Shi (PayPal Cyber Security Team)