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CRITICAL

GHSA-rxrv-835q-v5mh

locutus is vulnerable to Prototype Pollution

Quick fix

GHSA-rxrv-835q-v5mh — locutus: upgrade to the fixed version with the command below.

npm install locutus@2.0.39

Details

### 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 application that processes attacker-controlled input using this `locutus.php.strings.parse_str` may be affected. It could potentially lead to the following problems: 1. Authentication bypass 2. Denial of service 3. Remote code execution (if polluted property is passed to sinks like eval or child_process)

Are you affected?

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Affected packages

npm/locutus
Introduced in: 2.0.12Fixed in: 2.0.39
Fixnpm install locutus@2.0.39

References