What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-02-04 · updated 2026-07-15
• Weakness: CWE-1321

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.

Affected products

• locutusjs locutus: from 2.0.12 before 2.0.39 — fixed in 2.0.39

How to fix

Upgrade to a fixed version: locutusjs locutus 2.0.39. Check the vendor advisory for mitigations.

References

• https://github.com/locutusjs/locutus/commit/042af9ca7fde2ff599120783e720a17f335bb01c
• https://github.com/locutusjs/locutus/security/advisories/GHSA-rxrv-835q-v5mh
• https://access.redhat.com/security/cve/CVE-2026-25521
• https://bugzilla.redhat.com/show_bug.cgi?id=2436950
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-25521.json

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