CVE-2026-25521
In versions from 2.0.12 to before 2.0.39, a prototype pollution vulnerability exists in locutus.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.32%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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 4.0
- 9.4 CRITICALCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
- EPSS
- 0.32% probability · 25th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-1321, CWE-915
- Affected
- locutus/locutus
- Source
- security-advisories@github.com
EPSS 0.3% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://github.com/locutusjs/locutus/commit/042af9ca7fde2ff599120783e720a17f335bb01cPatch
- https://github.com/locutusjs/locutus/security/advisories/GHSA-rxrv-835q-v5mhExploit, Vendor Advisory
- 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
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.