Skip to content
Fencer Intel
critical 9.3

CVE-2026-25521 json

Locutus is vulnerable to Prototype Pollution

published 9mo ago modified last mo. also EUVD-2026-5340 , GHSA-rxrv-835q-v5mh

cvss
9.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 24%
public exploits
0
none known

Summary

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.

Patch / fix

  • npm locutus 2.0.39
  • locutus locutus 2.0.39

Is CVE-2026-25521 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-25521 updated cvss 9.3

locutus: Locutus is vulnerable to Prototype Pollution

  • Red Hat Logging Subsystem for Red Hat OpenShift openshift-logging/kibana6-rhel8, openshift-logging/elasticsearch6-rhel9, openshift-logging/logging-curator5-rhel9, openshift-logging/elasticsearch-proxy-rhel9, openshift-logging/elasticsearch-rhel9-operator, openshift-logging/elasticsearch-operator-bundle
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
9mo ago

Exploit prediction

0.31% chance of exploitation in the next 30 days, higher than 24% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • github.com https://github.com/locutusjs/locutus/security/advisories/GHSA-rxrv-835q-v5mh referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 9.4 CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
CISA ADP 3.1 9.3 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
CNA 4.0 9.4 CVSS: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/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 8.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
CNA 3.1 9.3 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
npm locutus
>=2.0.12, <2.0.39
2.0.39

Affected products

  • locutusjs locutus
  • Red Hat Logging Subsystem for Red Hat OpenShift

Classification

Weakness
  • CWE-1321 Improperly Controlled Modification of Object Prototype Attributes
  • CWE-915 Improperly Controlled Modification of Dynamically-Determined Object Attributes

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.