CVE-2026-33994 (GCVE-0-2026-33994)
Vulnerability from cvelistv5 – Published: 2026-03-27 22:15 – Updated: 2026-04-01 13:45
VLAI
EPSS
VEX
Title
Locutus Prototype Pollution due to incomplete fix for CVE-2026-25521
Summary
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.
Severity
9.8 (Critical)
SSVC
Exploitation: poc
Automatable: yes
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-04-01 13:45 UTC
CWE
- CWE-1321 - Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Assigner
GitHub_M
CNA
References
4 references
| URL | Tags |
|---|---|
| https://github.com/locutusjs/locutus/security/adv… | x_refsource_CONFIRM |
| https://github.com/locutusjs/locutus/pull/597 | x_refsource_MISC |
| https://github.com/locutusjs/locutus/commit/345a6… | x_refsource_MISC |
| https://github.com/locutusjs/locutus/releases/tag… | x_refsource_MISC |
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Browse all ATT&CK techniques and the vulnerabilities related to each.
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