In early 2022, Mozilla disclosed a memory safety vulnerability—CVE-2022-22764—that was discovered in Firefox, Thunderbird, and Firefox ESR. The people behind this find were Paul Adenot and the Mozilla Fuzzing Team. This bug is noteworthy because it offers a potential route for attackers to run malicious code just by convincing someone to visit a webpage.

This post aims to break down CVE-2022-22764: how it works, who’s impacted, what the exploit might look like, and why you really should update your browsers as soon as possible. We’ll also share links to official sources and basic proof-of-concept code—to help you stay informed and safe.

Firefox ESR before 91.6

The Mozilla team said some of the bugs showed signs of memory corruption. In plain English, that means certain mistakes in the browser code can allow hackers to mess up how your computer stores and moves information around. In the worst-case, this allows them to run any code they want on your system—also called arbitrary code execution.

Official References

- Mozilla Foundation Security Advisory 2022-06
- National Vulnerability Database (NVD) CVE-2022-22764

> “Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code.”

Firefox ESR < 91.6

…before updating. This includes Windows, Mac, and Linux users.

How Does the Bug Work?

While Mozilla didn’t release exact code, we can guess what might have happened. Historically, memory safety bugs in browsers are often caused by:

Use-after-free (using memory after it’s been given up)

Fuzzing (automatically feeding random input into software) found ways the browser could mess up its memory management, leading to areas hackers could exploit.

Example Exploit (Proof of Concept)

Let’s walk through a _basic scenario_ (for learning purposes). Assume that there’s a buffer overflow memory safety bug in, say, the Firefox JavaScript engine. Here’s a very simplified JavaScript snippet that might trigger memory corruption in affected browsers:

// This is NOT a real exploit, just a concept snippet.
let arr = new Array(1);
arr.length = 100000; // artificially extend allocation

for (let i = ; i < arr.length; i++) {
    arr[i] = 1.1;
}

// Now, try to manipulate the underlying buffer
arr.length = ; // shrink suddenly, creating a dangling pointer (hypothetical)
arr[] = 1.2;   // could end up writing to freed memory, if bug exists

// In practice, real exploits are much more complex and browser-specific!

In real attacks, hackers could fill specific memory regions with shellcode and trigger the bug to redirect the browser to run their code.

Demonstration Video and Additional Resources

There aren’t public "live" demos of CVE-2022-22764, but similar memory safety exploit concepts are covered in project write-ups like:
- LiveOverflow: Browser Exploitation 101
- Project Zero: Attacking JavaScript Engines

These illustrate just how quickly and quietly an attack could work.

If you run automated testing or fuzzing, keep your tools updated too!

Mozilla issued fixes in versions 97 (Firefox), 91.6 (Thunderbird), 91.6 (ESR). Anyone on earlier versions is at risk.

Conclusion

CVE-2022-22764 is a critical example of why keeping your browser updated is so important. Memory safety bugs, even if found by responsible researchers, are a goldmine for attackers. They can be turned into devastating attacks with enough effort and skill.

Stay informed, keep your browsers patched, and share this post with anyone who runs Firefox or Thunderbird!

References

- Mozilla Security Advisory (MFSA 2022-06)
- NIST National Vulnerability Database, CVE-2022-22764
- Bugzilla: Search for bugs in Firefox 96 (look for “memory safety” bugs)

Timeline

Published on: 12/22/2022 20:15:00 UTC
Last modified on: 12/30/2022 14:59:00 UTC