CVE-2024-29041: Express.js Open Redirect Vulnerability in Versions Prior to 4.19. and Pre-Release 5. Affects Minimalist Web Framework for Node

Express.js, a popular minimalist web framework for Node.js, has been found to be vulnerable to an open redirect issue in its handling of malformed URLs. The vulnerability affects all versions prior to 4.19. and pre-release alpha and beta versions of 5.. When a user of Express performs a redirect using a user-provided URL, Express performs an encode using encodeurl on the contents before passing it to the location header. However, this can lead to open redirect problems due to bypassing an allow list in Express applications, a critical security concern.

Exploit Details

The vulnerability is caused by the incorrect implementation of the encodeurl library in the redirect function in Express.js. The main method affected is res.location(), but this is also called from within res.redirect().

Here is a code snippet demonstrating the vulnerability

// Example Express.js application
const express = require('express');
const app = express();

// Route with redirect code
app.get('/redirect', (req, res) => {
  const url = req.query.url || '/';
  res.redirect(url);
});

// Server listening on port 300
app.listen(300, () => {
  console.log('Example app listening on port 300!');
});

In this example, an attacker could provide a malformed URL, and if the application is using an improperly implemented allow list, the attacker could exploit the open redirect vulnerability.

How to Remediate

To fix this vulnerability, update Express.js to version 4.19.2 or 5..-beta.3. These versions contain patches that address the open redirect vulnerability.

For example, you would update your package.json to include

"dependencies": {
  "express": "^4.19.2"
}

Or for Express 5..-beta.3

"dependencies": {
  "express": "^5..-beta.3"
}

After updating the version, rerun npm install to apply the changes. If you cannot update to the latest version, you should consider implementing additional input validation to ensure that only allowed URLs are accepted as input.

Conclusion

It is important to keep your dependencies up-to-date to protect against known vulnerabilities. In the case of the Express.js open redirect issue (CVE-2024-29041), updating to version 4.19.2 or 5..-beta.3 will help ensure the security of your application and protect against exploitation. Additionally, using proper input validation practices will further secure your application by ensuring only allowed URLs are accepted and processed.

Timeline

Published on: 03/25/2024 21:15:46 UTC
Last modified on: 03/26/2024 12:55:05 UTC