dbcve.org
LocutusApplication

CVE-2026-33994

CRITICAL · 9.8 CVSS v3.1 Published 2026-03-27
Fix available
A fix is available. Upgrade to 3.0.25 or later.
See remediation →
100/100
Remediation priority · Urgent
Public exploit Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

This is a prototype pollution vulnerability in the locutus npm package's `parse_str` function. The vulnerability stems from an incomplete fix for CVE-2026-25521 — the original `String.prototype.includes()` guard was replaced with a `RegExp.prototype.test()` guard, but since both are writable prototype methods, an attacker can still override `RegExp.prototype.test` to bypass the guard and pollute `Object.prototype` via crafted query strings.

MitigationUpgrade locutus to version 3.0.25 or later, which contains an updated fix that properly addresses the prototype pollution vulnerability.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
LocutusApplication
Affected:>= 2.0.39, < 3.0.25

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Locate locutus installation
    Run 'npm list locutus' or check package.json dependencies to see if locutus is installed
    Affected if locutus is listed as a dependency with version >= 2.0.39 and < 3.0.25
  2. Identify parse_str usage
    Search codebase for imports or requires of 'locutus' and usage of 'parse_str' function, e.g., grep for 'parse_str' or 'locutus/php/url/parse_str'
    Affected if Code calls the parse_str function from locutus
  3. Verify vulnerable code pattern
    Inspect node_modules/locutus/src/php/url/parse_str.js and look for RegExp.prototype.test usage in the guard logic
    Affected if The guard uses RegExp.prototype.test (the vulnerable pattern replacing the earlier String.prototype.includes)
  4. Assess input source
    Trace how data reaches parse_str , check if query string parameters or user-controlled URL parameters are passed to this function
    Affected if User-supplied query string data flows directly into parse_str without sanitization

You are affected if locutus version is >= 2.0.39 and < 3.0.25, the parse_str function is used, and untrusted input can be passed to it.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 3.0.25 or later
Fixed in 3.0.25
Vendor patch github.com →
Interim mitigation

Upgrade locutus to version 3.0.25 or later, which contains an updated fix that properly addresses the prototype pollution vulnerability.

Recommended fix High confidence

3.0.25 or later

  1. Run `npm install [email protected]` or update the locutus dependency in package.json to version 3.0.25 or later
  2. Run `npm audit` to verify the vulnerability is resolved
  3. Test the parse_str function with the application's query string inputs to confirm expected behavior
Caveat Version jump from 2.x to 3.x may include breaking changes; review locutus changelog before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Locutus Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing3.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,210
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,936.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-33994 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-33994 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data