CVE-2026-33994

The record

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.

Affected packages

Related vulnerabilities

• GHSA-vc8f-x9pp-wf5p Locutus Prototype Pollution due to incomplete fix for CVE-2026-25521 Same vulnerability
• CVE-2026-33993 Locutus brings stdlibs of other programming languages to JavaScript for educational… Also affects locutus
• GHSA-4mph-v827-f877 Locutus has Prototype Pollution via __proto__ Key Injection in unserialize() Also affects locutus
• CVE-2026-32304 Locutus brings stdlibs of other programming languages to JavaScript for educational… Also affects locutus
• GHSA-vh9h-29pq-r5m8 Locutus vulnerable to RCE via unsanitized input in create_function() Also affects locutus
• CVE-2026-29091 Locutus brings stdlibs of other programming languages to JavaScript for educational… Also affects locutus
• GHSA-fp25-p6mj-qqg6 locutus call_user_func_array vulnerable to Remote Code Execution (RCE) due to Code… Also affects locutus
• CVE-2026-25521 Locutus brings stdlibs of other programming languages to JavaScript for educational… Also affects locutus