High severity · published Feb 4, 2026
CVE-2026-25521
Locutus is vulnerable to Prototype Pollution
8.8
CVSS
0.3%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 25% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
LO
locutus · locutusjs
>= 2.0.12, < 2.0.39 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-25521
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-25521
Patch
https://github.com/locutusjs/locutus/commit/042af9ca7fde2ff599120783e720a17f335bb01c
Exploit
https://github.com/locutusjs/locutus/security/advisories/GHSA-rxrv-835q-v5mh
access.redhat.com
https://access.redhat.com/security/cve/CVE-2026-25521
bugzilla.redhat.com
https://bugzilla.redhat.com/show_bug.cgi?id=2436950
security.access.redhat.com
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-25521.json
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