# CVE-2026-33994: Locutus prototype pollution in parse_str

Source: https://junglewise.ai/threats/cve-2026-33994-locutus-prototype-pollution-in-parse-str  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-03-27. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-33994 · Severity: critical · CVSS 9.8 · Published 2026-03-27

Locutus is a JavaScript library that provides PHP-compatible utility functions. A prototype pollution vulnerability in its parse_str function allows attackers to corrupt the base object prototype, potentially leading to authentication bypass, service disruption, or code execution in applications that process untrusted input with this library.

Technologies: [locutus (npm)](https://junglewise.ai/threats/technologies/locutus). Vendors: [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-33994 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-33994 being exploited in the wild.

**How severe is CVE-2026-33994?** Critical severity, with a CVSS score of 9.8, published 27 March 2026.

**Which products and versions are affected?** locutus (npm) SEMVER:introduced=2.0.39,fixed=3.0.25.

**Is there a fix for CVE-2026-33994?** Yes. locutus (npm): upgrade to 3.0.25 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-33994 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-33994?** Check whether you run Locutus or locutus (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- locutus (npm): upgrade to 3.0.25 or later

  ```sh
  npm install locutus@3.0.25
  ```


## Technical details

The parse_str function in Locutus contains a prototype pollution vulnerability stemming from an incomplete fix for CVE-2026-25521. The previous patch replaced a String.prototype.includes()-based guard with RegExp.prototype.test(), but RegExp.prototype.test is itself a writable method that can be overridden. An attacker can bypass the guard by first polluting RegExp.prototype.test (via a separate prototype pollution gadget in another npm package) to always return false, then passing a crafted query string like '__proto__[polluted]=yes' to parse_str, allowing them to corrupt Object.prototype. The fix shipped in version 3.0.25 removes dependency on prototype methods and instead hardens the assignment sink itself using direct string comparisons that cannot be overridden.

## Affected products

- Locutus Locutus 2.0.39 through 3.0.24

## Identifiers

- CVE-2026-33994
- GHSA-vc8f-x9pp-wf5p

## Timeline

- 2026-03-27: disclosed
- 2026-03-27: patched: Fixed in version 3.0.25
- 2026-03-27: advisory: GHSA-vc8f-x9pp-wf5p published

## References

- [https://github.com/locutusjs/locutus/security/advisories/GHSA-rxrv-835q-v5mh](https://github.com/locutusjs/locutus/security/advisories/GHSA-rxrv-835q-v5mh)
- [https://github.com/locutusjs/locutus/security/advisories/GHSA-vc8f-x9pp-wf5p](https://github.com/locutusjs/locutus/security/advisories/GHSA-vc8f-x9pp-wf5p)

## Related threats

- [Locutus prototype pollution via __proto__ injection in unserialize](https://junglewise.ai/threats/cve-2026-33993-locutus-prototype-pollution-via-proto-injection-in-unserialize)
- [Locutus code injection in create_function](https://junglewise.ai/threats/cve-2026-32304-locutus-code-injection-in-create-function)
- [Locutus remote code execution in call_user_func_array](https://junglewise.ai/threats/cve-2026-29091-locutus-remote-code-execution-in-call-user-func-array)
- [Locutus prototype pollution in parse_str function](https://junglewise.ai/threats/cve-2026-25521-locutus-prototype-pollution-in-parse-str-function)
- [Locutus escapeshellarg command injection](https://junglewise.ai/threats/cve-2020-13619-locutus-escapeshellarg-command-injection)