critical

CVE-2026-33994

locutus: Locutus: Prototype pollution vulnerability in parse_str function

Published 27 Mar 2026Modified 26 Oct 2026CWE 1321

In the Trivy database since at least 24 Oct 2026, 07:11 UTCWhen it arrived before that build is not recorded.

Severity by source

NVD9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

GHSA6.3CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N

Red Hat5.3CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Trivy's own label is CRITICAL. Rated critical by NVD. Rated lower by GHSA (medium), Red Hat (medium).

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.

Affected packages and fixed versions

Source	Package	Fixed in
npm::GitHub Security Advisory npm	locutus	3.0.25

References

All 9 references

https://www.cve.org/CVERecord?id=CVE-2026-33994

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