CVE-2026-33994
Locutus Prototype Pollution due to incomplete fix for CVE-2026-25521
Description
Locutus brings stdlibs of other programming languages to JavaScript for educational purposes. Starting in version 2.0.39 and prior to version 3.0.25, a prototype pollution vulnerability exists in the `parse_str` function of the npm package locutus. An attacker can pollute `Object.prototype` by overriding `RegExp.prototype.test` and then passing a crafted query string to `parse_str`, bypassing the prototype pollution guard. This vulnerability stems from an incomplete fix for CVE-2026-25521. The CVE-2026-25521 patch replaced the `String.prototype.includes()`-based guard with a `RegExp.prototype.test()`-based guard. However, `RegExp.prototype.test` is itself a writable prototype method that can be overridden, making the new guard bypassable in the same way as the original — trading one hijackable built-in for another. Version 3.0.25 contains an updated fix.
INFO
Published Date :
March 27, 2026, 11:17 p.m.
Last Modified :
Oct. 26, 2026, 10:10 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | CRITICAL | [email protected] | ||||
| CVSS 3.1 | CRITICAL | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update locutus to version 3.0.25 or later.
- Review and sanitize user inputs carefully.
- Implement robust input validation checks.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-33994.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-33994 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-33994
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-33994 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-33994 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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CVE Translated by [email protected]
Oct. 26, 2026
Action Type Old Value New Value Added Translation Title: locutus de locutusjs, Description: Locutus aporta librerías estándar de otros lenguajes de programación a JavaScript con fines educativos. A partir de la versión 2.0.39 y antes de la versión 3.0.25, existe una vulnerabilidad de contaminación de prototipos en la función “parse_str” del paquete npm locutus. Un atacante puede contaminar “Object.prototype” sobrescribiendo “RegExp.prototype.test” y luego pasando una cadena de consulta manipulada a “parse_str”, eludiendo la protección contra la contaminación de prototipos. Esta vulnerabilidad se deriva de una corrección incompleta para CVE-2026-25521. El parche de CVE-2026-25521 reemplazó la protección basada en “String.prototype.includes()” con una protección basada en “RegExp.prototype.test()”. Sin embargo, “RegExp.prototype.test” es en sí mismo un método de prototipo escribible que puede ser sobrescrito, haciendo que la nueva protección sea eludible de la misma manera que la original - intercambiando una función incorporada secuestrable por otra. La versión 3.0.25 contiene una corrección actualizada. -
CVE Modified by [email protected]
Jun. 17, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'locutusjs', 'product': 'locutus', 'versions': [{'status': 'affected', 'version': '>= 2.0.39, < 3.0.25'}]}] -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 17, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-33994', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'yes'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-04-01T13:45:33.039333Z'} -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Apr. 01, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H -
Initial Analysis by [email protected]
Apr. 01, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Added CPE Configuration OR *cpe:2.3:a:locutus:locutus:*:*:*:*:*:node.js:*:* versions from (including) 2.0.39 up to (excluding) 3.0.25 Added Reference Type GitHub, Inc.: https://github.com/locutusjs/locutus/commit/345a6211e1e6f939f96a7090bfeff642c9fcf9e4 Types: Patch Added Reference Type GitHub, Inc.: https://github.com/locutusjs/locutus/pull/597 Types: Issue Tracking Added Reference Type GitHub, Inc.: https://github.com/locutusjs/locutus/releases/tag/v3.0.25 Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/locutusjs/locutus/security/advisories/GHSA-vc8f-x9pp-wf5p Types: Exploit, Vendor Advisory Added Reference Type GitHub, Inc.: https://github.com/locutusjs/locutus/security/advisories/GHSA-vc8f-x9pp-wf5p Types: Exploit, Vendor Advisory Added Reference Type GitHub, Inc.: https://github.com/locutusjs/locutus/security/advisories/GHSA-vc8f-x9pp-wf5p Types: Exploit, Vendor Advisory Added Reference Type GitHub, Inc.: https://github.com/locutusjs/locutus/security/advisories/GHSA-vc8f-x9pp-wf5p Types: Exploit, Vendor Advisory -
New CVE Received by [email protected]
Mar. 27, 2026
Action Type Old Value New Value Added Description Locutus brings stdlibs of other programming languages to JavaScript for educational purposes. Starting in version 2.0.39 and prior to version 3.0.25, a prototype pollution vulnerability exists in the `parse_str` function of the npm package locutus. An attacker can pollute `Object.prototype` by overriding `RegExp.prototype.test` and then passing a crafted query string to `parse_str`, bypassing the prototype pollution guard. This vulnerability stems from an incomplete fix for CVE-2026-25521. The CVE-2026-25521 patch replaced the `String.prototype.includes()`-based guard with a `RegExp.prototype.test()`-based guard. However, `RegExp.prototype.test` is itself a writable prototype method that can be overridden, making the new guard bypassable in the same way as the original — trading one hijackable built-in for another. Version 3.0.25 contains an updated fix. Added CVSS V4.0 AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N/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 Added CWE CWE-1321 Added Reference https://github.com/locutusjs/locutus/commit/345a6211e1e6f939f96a7090bfeff642c9fcf9e4 Added Reference https://github.com/locutusjs/locutus/pull/597 Added Reference https://github.com/locutusjs/locutus/releases/tag/v3.0.25 Added Reference https://github.com/locutusjs/locutus/security/advisories/GHSA-vc8f-x9pp-wf5p Added Reference https://github.com/locutusjs/locutus/security/advisories/GHSA-vc8f-x9pp-wf5p