CVE-2022-0459 was a serious security vulnerability discovered in Google Chrome, specifically affecting Chrome versions before 98..4758.80. This flaw, found in the browser’s *Screen Capture* feature, allowed attackers to exploit a “use-after-free” bug, potentially leading to *heap corruption* and more severe consequences, such as executing arbitrary code on the victim’s machine.

In this post, I’ll break down what this CVE means, how it could be exploited, share sample code, and provide links for further reading. This will be especially useful for anyone interested in browser security, exploit development, or just keeping their systems safe.

What is a Use-After-Free?

A use-after-free bug occurs when a program continues to use a portion of memory after it has been “freed” (deleted or released). In practical terms, this can let attackers manipulate objects in memory, causing unexpected behavior – like executing malicious code.

What Went Wrong in Chrome’s Screen Capture?

Chrome’s *Screen Capture* feature lets websites record what’s shown on your screen or in a particular browser tab. If a website convinced you to start screen capture (by clicking a button, for example), and the attacker could trigger the use-after-free bug, they could corrupt Chrome’s memory.

The root of CVE-2022-0459 was that, under certain circumstances, the renderer (the Chrome component that displays websites) could free memory that was still being used during screen capture operations. An attacker could craft a malicious HTML page to setup and exploit this condition, especially if they already gained code execution in the renderer process—often through another vulnerability or a malicious extension.

Here’s a simplified step-by-step scenario showing how an attacker could exploit this vulnerability

1. Compromise the Renderer: The attacker already has code execution in the Chrome renderer (e.g., from another vulnerability).
2. Lure User to Interact: The attacker crafts an HTML page with tricky JavaScript that convinces a user to start a screen capture session—perhaps by clicking “Share screen.”
3. Trigger Use-After-Free: The attacker’s code rapidly allocates, frees, and re-uses memory tied to the screen capture object. This creates a window where freed memory is still accessed, leading to heap corruption.
4. Gain Further Control: If successful, the attacker may corrupt memory in a way that lets them execute arbitrary code—perhaps escaping Chrome’s sandbox or escalating privileges.

Proof-of-Concept Example

Below is an intentionally over-simplified JavaScript snippet mimicking how an attacker could try to mess with memory by quickly creating and destroying video streams and elements.

Note: This is not a real exploit, but illustrates the general approach

// User is convinced to click a button to start capture
document.getElementById('captureBtn').onclick = async function() {
  let stream = await navigator.mediaDevices.getDisplayMedia({ video: true });

  // Rapid creation & destruction
  let victimVideo = document.createElement('video');
  victimVideo.srcObject = stream;
  document.body.appendChild(victimVideo);

  // Attacker removes the element to free memory
  setTimeout(() => {
    document.body.removeChild(victimVideo);
    // Attacker now reallocates memory hoping Chrome reuses freed memory
    let spray = [];
    for (let i = ; i < 10000; i++) {
      spray.push(document.createElement('div'));
    }
    // ...further heap manipulation here
  }, 10);
};

Again, a real-world exploit would be far more complicated and tightly targeted.

How Was This Fixed?

Chrome’s developers patched this issue by better managing the lifetime of objects tied to screen capture. After the update, freeing the underlying resources no longer leaves dangling references. This means that even if a programmer tries to use freed memory, the browser’s new checks prevent it.

How to Protect Yourself

- Update Chrome: Make sure you’re running Chrome version 98..4758.80 or later. Go to chrome://settings/help to check and update.

Be Careful with Extensions: Only install browser extensions you trust.

- Watch for Social Engineering: Don’t click “Allow” on screen sharing requests unless you really trust the webpage.

References and Further Reading

- Chromium Bug Tracker: Issue 1292277  
- Google Chrome Release Notes for v98..4758.80
- CVE-2022-0459 at NIST NVD
- Project Zero’s blog: Introduction to Use-After-Free Exploits

Conclusion

*CVE-2022-0459* is an example of how a single programming error in something as everyday as screen sharing could give attackers a serious foothold, especially if combined with other vulnerabilities. That’s why it’s crucial to keep browsers updated and be careful where you click.

Timeline

Published on: 04/05/2022 01:15:00 UTC
Last modified on: 04/11/2022 09:38:00 UTC