How severe is CVE-2026-25521?

CVE-2026-25521 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-25521 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (17th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-25521?

CVE-2026-25521 affects Locutus. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-25521?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-25521 have an EU (EUVD) identifier?

Yes. CVE-2026-25521 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-5340.

When was CVE-2026-25521 published?

CVE-2026-25521 was published on 2026-02-04 and last updated on 2026-06-27.

CVE-2026-25521

CVE-2026-25521 is a high-severity vulnerability in Locutus with a CVSS 3.x base score of 8.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-1321.

Key facts

Severity: High (CVSS 3.x base score 8.8)
CVSS v4: 9.4
EPSS exploit prediction: 0% (17th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-5340
Weakness: CWE-1321
Affected product: Locutus
Published: 2026-02-04
Last modified: 2026-06-27

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.

Frequently asked questions

What is CVE-2026-25521?: 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.
How severe is CVE-2026-25521?: CVE-2026-25521 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-25521 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (17th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-25521?: CVE-2026-25521 affects Locutus. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-25521?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-25521 have an EU (EUVD) identifier?: Yes. CVE-2026-25521 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-5340.
When was CVE-2026-25521 published?: CVE-2026-25521 was published on 2026-02-04 and last updated on 2026-06-27.

References

Affected products (1)

cpe:2.3:a:locutus:locutus:*:*:*:*:*:node.js:*:*

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