---
id: CVE-2026-93753
title: >-
  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
summary: >-
  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…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N'
cwe:
  - CWE-1321
vendor: TehShrike
product: deepmerge
affected:
  - deepmerge <= 4.3.1
published: '2026-09-18'
updated: '2026-09-23'
sourceUpdated: '2026-09-23T17:17:50.017'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-93753'
references:
  - url: 'https://github.com/TehShrike/deepmerge'
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/TehShrike/deepmerge/blob/5b87756a5671635679001cbac72aa42f23472c81/index.js#L39-L60
    label: disclosure@vulncheck.com
  - url: 'https://github.com/TehShrike/deepmerge/issues/273'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/deepmerge-through-4.3.1-prototype-poisoning-via-mergeobject
    label: disclosure@vulncheck.com
  - url: 'https://github.com/TehShrike/deepmerge/issues/273'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
  - cve.org
  - exploit-available
epss: 0.00514
epssPercentile: 0.41236
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-18T19:16:56.102337Z'
ingestedAt: '2026-09-18T18:47:53.270Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.