CVE-2022-4179 - Understanding the Use-After-Free Audio Exploit in Google Chrome (Before Version 108..5359.71)

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Introduction

When we hear about browser security flaws, most of us worry about phishing or sketchy downloads. But sometimes, the real threats come from deep within your browser—like how audio is managed in Chrome. In this long read, we'll break down a real-world vulnerability, explain how attackers might use it, and give you a detailed look at the bug CVE-2022-4179. Whether you’re a budding cybersecurity enthusiast or just curious about how browsers can be hacked, you’ll get a clear picture here—no jargon, just the essentials.

What is CVE-2022-4179?

CVE-2022-4179 is a security bug in Google Chrome’s Audio component. Before version 108..5359.71, some mishandled code allowed for what's called a "Use-After-Free (UAF)" vulnerability. This is a classic type of bug where the program keeps using memory even after it's been freed up, which can lead to all sorts of bad things—like letting attackers run their own code on your computer.

In this case:
If you installed a malicious Chrome extension, an attacker could exploit this bug to corrupt the browser’s memory. This can lead to running unwanted code—potentially letting the attacker take control of your browser, steal info, or worse.

- Bug Summary: Use after free in Audio in Google Chrome prior to 108..5359.71 allowed an attacker who convinced a user to install a malicious extension to potentially exploit heap corruption via a crafted Chrome Extension. (Chromium security severity: High)

References

- Google Chrome Security Advisory
- Chromium Bug Tracker ID 1378493
- CVE Details - CVE-2022-4179

What is a Use-After-Free Bug?

Let’s take a closer look. In programming, especially in languages like C++, you often have to manually manage memory—ask the system for some, use it, then eventually tell the system you’re done with it ("free" it). A UAF bug happens when code tries to keep using that memory after it’s already been given back and potentially taken over or changed by something else.

This is dangerous: attackers can try to control what’s put in that old memory spot, and when your program uses it, they can sneak in their own instructions.

Audio Component in Chrome

Chrome’s Audio system is responsible for playing sounds and managing audio streams in its tabs and extensions. An attacker who tricks you into installing a dodgy Chrome extension could potentially interact with the Audio API in unexpected ways, triggering the bug.

Prepare Malicious Extension:

The attacker creates a Chrome extension loaded with code to interact with the audio API in a way that triggers the use-after-free bug.

Trigger Vulnerability:

The extension starts audio operations (possibly starting and stopping streams, changing settings rapidly). The bug is that Chrome may free a memory object but then tries to use it again after it’s already been returned to the system.

Exploit Heap Corruption:

During this window, the extension arranges for the freed memory area to be occupied by data crafted by the attacker. When Chrome accesses the “freed” memory, it instead executes the attacker's instructions.

Code Execution:

In the worst case, this could allow running code *in the context of the browser*, possibly reading your data or running commands.

Here’s a simple (hypothetical) illustration in pseudo-code to show how this kind of bug can happen

class AudioStream {
public:
    void play();
    void stop();
    // ... other methods
};

void badFunction() {
    AudioStream* stream = new AudioStream();

    stream->play();
    delete stream; // Free the memory

    stream->stop(); // Oops! Using memory that was just freed
}

In Chrome, this would be much more complex and hidden within millions of lines of code, but the principle is the same.

Proof of Concept (PoC) Approach

> Note: Responsible disclosure in action—we won’t give a real exploit, but here’s how attackers would typically approach this:

Quickly reallocate that memory (using Javascript ArrayBuffers, for example);

4. When Chrome tries to access the just-freed object—boom, attacker-controlled data is used by the browser.

How was it Fixed?

The official fix patched the reference handling in the Audio component, making sure memory isn’t accessed after being freed.

- GitHub Patch Sample: GitHub Chromium Patch

Conclusion

CVE-2022-4179 is a great case study of how deep browser bugs can be triggered by something as simple as a suspicious Chrome extension. It shows just how important it is to keep your browser and extensions up to date, and how even trusted software can be vulnerable.

Stay safe—only trust extensions with good reputations, run regular updates, and don’t ignore those Chrome restart prompts!

Timeline

Published on: 11/30/2022 00:15:00 UTC
Last modified on: 05/03/2023 12:16:00 UTC