CVE-2026-25521
Prototype pollution in Locutus JS lib (2.0.12–2.0.38); fixed in 2.0.39.
Is CVE-2026-25521 being exploited?
Not confirmed. CVE-2026-25521 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.29% probability of exploitation in the next 30 days.
How severe is CVE-2026-25521?
CVE-2026-25521 is rated Critical with a CVSS score of 9.4. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-25521?
Yes. A fix has been recorded for CVE-2026-25521. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-25521 affect?
CVE-2026-25521 affects Locutus JS library, Versions 2.0.12–2.0.38. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-25521?
Upgrade to 2.0.39; verify app for polluted prototypes.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Pollutes Object.prototype via crafted input; enables property override and potential RCE/DoS in apps using Locutus.
Patch when possible
- affected>= 2.0.12 and < 2.0.39
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.