CVE-2026-93753CWE-1321

CVE-2026-93753

High · published September 18, 2026

CVSS v3.1
7.5
EPSS
1%
Percentile
43.0
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
7.5 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
CVSS v4.0
8.7 · 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
EPSS
0.00514 · 43.0th percentile
Weakness
CWE-1321 · Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Published
2026-09-18T22:18Z
References (5)
https://github.com/TehShrike/deepmerge · [email protected]https://github.com/TehShrike/deepmerge/blob/5b87756a5671635679001cbac72aa42f23472c81/index.js#L39-L60 · [email protected]https://github.com/TehShrike/deepmerge/issues/273 · [email protected]https://www.vulncheck.com/advisories/deepmerge-through-4.3.1-prototype-poisoning-via-mergeobject · [email protected]https://github.com/TehShrike/deepmerge/issues/273 · 134c704f-9b21-4f2e-91b3-4a467353bcc0
EPSS history
Timeline
  • 20 SEP 03:25Z
    EPSS moved — → 0%
    epss
  • 18 SEP 17:51Z
    deepmerge through 4.3.1 Prototype Poisoning via mergeObject
    cvelistv5