CVE-2024-51479: Next.js Authorization Bypass Vulnerability in Middleware Based on Pathname

Next.js is a popular React framework that allows developers to build full-stack web applications with ease. Recently, a vulnerability (CVE-2024-51479) was discovered in certain versions of Next.js that could potentially lead to unauthorized access of sensitive information. This post provides an in-depth look at the vulnerability, including how it is exploited, and steps to remediate it.

Exploit Details

In affected versions of Next.js, if an application is performing authorization checks in middleware based on pathname, it's possible for attackers to bypass these checks for pages directly under the application's root directory. This means that the following scenarios are possible:

- [Not affected] https://example.com/
- [Affected] https://example.com/foo
- [Not affected] https://example.com/foo/bar

To better understand this vulnerability, consider the following example code snippet.

Example Code Snippet

import { useRouter } from 'next/router';

function MyApp({ Component, pageProps }) {
  const router = useRouter();

  useEffect(() => {
    if (!isAuthorizedUser() && router.pathname.startsWith('/foo')) {
      router.push('/login');
    }
  }, [router.pathname]);

  return <Component {...pageProps} />;
}

export default MyApp;

In this example, the application checks for user authorization using isAuthorizedUser() function, and if the user is not authorized, they are redirected to the /login page. Theoretically, this should secure the /foo directory, but due to the vulnerability, this protection can be bypassed.

Solution and Mitigation

This issue has been resolved in Next.js version 14.2.15. To patch the vulnerability, simply update your Next.js installation to this version or later using the following command:

npm install next@latest

It's also important to note that if your Next.js application is hosted on Vercel, this vulnerability has already been automatically mitigated, regardless of your Next.js version.

For more details on this vulnerability, you can consult the official CVE entry for CVE-2024-51479

- CVE-2024-51479

Additional information regarding the vulnerability and patch can be found in Next.js and Vercel's official documentation:

- Next.js Changelog
- Vercel Security Post

Conclusion

CVE-2024-51479 is a potentially serious issue for developers using certain versions of Next.js, but it can be easily remediated by updating to Next.js 14.2.15 or later. If your Next.js application is hosted on Vercel, they have already taken care of the vulnerability for you, but it is recommended to update Next.js as a best practice. By taking these steps, you can help ensure that your web applications are secure and your users' data is protected.

Timeline

Published on: 12/17/2024 19:15:06 UTC