CVE-2026-33994
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.
- CVSS 4.0
- 6.3
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N - CVSS 3.1
- 9.8
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - EPSS
- 0.6% chance of exploitation in the next 30 days; higher than 46% of CVEs (scores of 2026-10-26)
- CWE
- CWE-1321
- Published
- Modified
- Record from
- the NVD, synced
Affected
- locutus:locutus
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-vc8f-x9pp-wf5p | npm | locutus | >=2.0.39 <3.0.25 | 3.0.25 |
References
- https://github.com/locutusjs/locutus/commit/345a6211e1e6f939f96a7090bfeff642c9fcf9e4
- https://github.com/locutusjs/locutus/pull/597
- https://github.com/locutusjs/locutus/releases/tag/v3.0.25
- https://github.com/locutusjs/locutus/security/advisories/GHSA-vc8f-x9pp-wf5p
- https://github.com/locutusjs/locutus/security/advisories/GHSA-vc8f-x9pp-wf5p