CVE-2026-93753
deepmerge through 4.3.1 Prototype Poisoning via mergeObject
- State
- Published
- Severity
- 8.7 High
- Published
- Sep 18, 2026
- Updated
- Sep 24, 2026
- Reserved
- Sep 18, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 8.7 High | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N | VulnCheck |
| 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N | VulnCheck |
Weaknesses
- CWE-1321 Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Affected Products
| Product | Versions |
|---|---|
deepmergeTehShrike |
|
References
- GitHub Issue #273issue-tracking
- https://github.com/TehShrike/deepmergeproduct
- propertyIsUnsafe() target-shape guard and the ungated target copy looptechnical-description
- VulnCheck Advisory: deepmerge through 4.3.1 Prototype Poisoning via mergeObjectthird-party-advisory
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