GHSA-gcqx-w48m-w2h4

Suggest an improvement
Source
https://github.com/advisories/GHSA-gcqx-w48m-w2h4
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-gcqx-w48m-w2h4/GHSA-gcqx-w48m-w2h4.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-gcqx-w48m-w2h4
Aliases
Published
2026-09-18T18:31:44Z
Modified
2026-10-27T21:45:04Z
Severity
  • 5.3 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N CVSS Calculator
  • 2.7 (Low) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U CVSS Calculator
Summary
deepmerge mergeObject() allows prototype poisoning of returned objects
Details

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.

Database specific 
{
    "cwe_ids":  [
        "CWE-1321"
    ],
    "github_reviewed":  true,
    "github_reviewed_at":  "2026-10-27T21:34:55Z",
    "nvd_published_at":  "2026-09-18T18:18:34Z",
    "severity":  "LOW"
}
References

Affected packages

npm / deepmerge

Package

Name
deepmerge
View open source insights on deps.dev
Purl
pkg:npm/deepmerge

Affected ranges

Type
SEMVER
Events
Introduced
4.2.0
Last Affected
4.3.1

Database specific

source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-gcqx-w48m-w2h4/GHSA-gcqx-w48m-w2h4.json"