CVE-2026-25521 CRITICAL

CVE-2026-25521: Locutus is vulnerable to Prototype Pollution

Vendor Locutusjs
Product locutus
Weakness CWE-1321
Published February 4, 2026
Last update June 29, 2026

CVSS base score

9.4/10
Attack vector Local
Attack complexity Low
Privileges required None
User interaction None
Confidentiality
Integrity

CVSS vector

CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

What the vulnerability does

01Description

Locutus brings stdlibs of other programming languages to JavaScript for educational purposes. In versions from 2.0.12 to before 2.0.39, a prototype pollution vulnerability exists in locutus. Despite a previous fix that attempted to mitigate prototype pollution by checking whether user input contained a forbidden key, it is still possible to pollute Object.prototype via a crafted input using String.prototype. This issue has been patched in version 2.0.39.

Key dates

02Disclosure timeline

February 4, 2026 CVE published
June 29, 2026 Record updated