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Security Issue in Next.js Middleware: What You Need to Know


This content originally appeared on DEV Community and was authored by iheb-sebai

Hey developers! 👋 If you’re using Next.js, there’s something important you should know—a recent security issue in middleware could put your app at risk. But don’t worry, I’ll break it down simply and show you how to fix it. Let’s dive in! 🚀

What Happened?

A vulnerability was found in Next.js middleware that lets attackers sneak past authentication and authorization checks. In simple terms, someone could gain access to parts of your app that should be protected. Not cool, right? 😬

Who Is Affected?

If your project is running Next.js versions:

  • 11.1.4 to 13.5.6
  • 14.0.0 to 14.2.24
  • 15.0.0 to 15.2.2

Then your app is at risk, and you need to act fast! ⏳

How Does the Attack Work?

The problem comes from an internal HTTP header called x-middleware-subrequest. It was meant to help Next.js handle requests inside middleware, but hackers found a way to manipulate it and skip security checks. That means they could access private pages or data they shouldn’t see. Yikes! 😱

How to Fix It?

Good news! 🎉 Next.js has released fixes, so all you need to do is update your app. Here’s how:

  1. Update Next.js to the latest version

    • If you’re using Next.js 15.x, update to 15.2.3
    • If you’re using Next.js 14.x, update to 14.2.25
    • If you’re using Next.js 13.x, update to 13.5.9
    • If you’re using Next.js 12.x, update to 12.3.5

  2. Check Your Middleware Code 🧐

    • Don’t rely only on middleware for security.
    • Make sure your backend and API routes also have proper authentication.

  3. Stay Alert 🔍

    • Keep an eye on your server logs for any suspicious activity.
    • Use security tools to catch potential threats before they become real problems.

Why This Matters

Security is everything! 🛡 Keeping your Next.js app updated and secure protects your users, your data, and your reputation. No one wants to deal with a security breach, so take a few minutes to update and check your app today.

If you’re using Next.js, don’t wait—update now and stay safe out there! 🚀


This content originally appeared on DEV Community and was authored by iheb-sebai