High 7.5Published Sep 18, 2026

CVE-2026-93753deepmerge through 4.3.1 Prototype Poisoning via mergeObject

Updated under an hour ago (2026-10-19 10:23 UTC)

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It affects TehShrike deepmerge. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for TehShrike deepmerge

Exploited in the last 30 days

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.

CVSS: 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness (CWE): CWE-1321
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: VulnCheck
NVD analysis: Deferred
Record last updated: Sep 24, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

TehShrike deepmerge tehshrike:deepmerge (from the name)	through 4.3.1	CNA record

References

https://github.com/TehShrike/deepmerge/issues/273issue-tracking
https://github.com/TehShrike/deepmergeproduct
https://github.com/TehShrike/deepmerge/blob/5b87756a5671635679001cbac72aa42f23472c81/index.js#L39-L60technical-description
https://www.vulncheck.com/advisories/deepmerge-through-4.3.1-prototype-poisoning-via-mergeobjectthird-party-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.