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CVE-2026-25521

Locutus vulnerability

8.8 HIGHPublic exploitEPSS 0.50%
  1. Published4 Feb 2026

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 3.1 breakdown

Attack vectorLocal
Attack complexityLow
Privileges requiredLow
User interactionNone
ScopeChanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Affected products

Locutus≥ 2.0.12 < 2.0.39

Remediation

Fixed in
Locutus≥ 2.0.39

References

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Frequently asked

Is CVE-2026-25521 being actively exploited?

CVE-2026-25521 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.50%.

How severe is CVE-2026-25521?

CVE-2026-25521 has a CVSS 3.1 base score of 8.8, rated high. EPSS estimates a 0.50% probability of exploitation.

Which products are affected by CVE-2026-25521?

Affected products include Locutus.

How do I fix CVE-2026-25521?

Upgrade affected software to a fixed version, for example Locutus 2.0.39 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.