Mozilla’s Firefox is one of the most popular open-source browsers available, used by millions around the world. But, like any software, it sometimes suffers from security issues that could put users at risk. In late 2021, Mozilla security researchers uncovered CVE-2022-22751, a set of dangerous memory safety vulnerabilities that could potentially let hackers run arbitrary code on your computer if you’re running certain outdated versions of Firefox or Thunderbird. In this long read, we’ll break down what CVE-2022-22751 is, how it works, and why you need to update—using plain, straightforward language.

Thunderbird 91.4 and earlier

These bugs were discovered by a team of Mozilla’s own developers, including Calixte Denizet, Kershaw Chang, Christian Holler, Jason Kratzer, Gabriele Svelto, Tyson Smith, Simon Giesecke, and Steve Fink.

Memory Safety Bugs? What Are Those?

A *memory safety* bug is a type of software bug that happens when a program incorrectly manages computer memory—something computers use to temporarily store information as they run programs. When memory safety issues exist, it’s sometimes possible for attackers to trick software into doing things it shouldn’t, such as running their code on your machine. This is often the first step toward more severe attacks.

Thunderbird < 91.5

If you’re using any of these, updating immediately is essential.

Run malicious code on your system (Remote Code Execution)

With CVE-2022-22751, Mozilla says “with enough effort some of these [bugs] could have been exploited to run arbitrary code.” In security terms, that's very serious—it means a malicious web page or email could potentially take over your computer if exploited correctly.

Simplified Example: The Danger of Memory Corruption

The Mozilla advisory doesn’t release proof-of-concept code, but let’s look at a simple, general example in C++ to understand how memory safety bugs might look in code:

char buffer[10];
strcpy(buffer, userInput); // Unsafe: if userInput > 10 chars, memory gets corrupted!

When a browser exposes a bug like this deep in its code, attackers might trigger it by crafting weird web content or emails.

An attacker could craft a malicious website.

- The site would use special code, data, or images to trigger the memory bug in Firefox or Thunderbird.
- If successful, the bug could “corrupt” part of your computer’s memory, “breaking out” of the browser and running whatever the attacker wants—potentially stealing files, installing malware, or even spying on you.

Real-World Example

While the full technical details and exploits are not public—to protect users—Mozilla’s historical advisories make it clear memory bugs are a real risk. Here’s a paraphrased, simplified attack flow:

The fix is simple

- Update Firefox or Thunderbird to the latest version. Mozilla patched these bugs quickly, so versions *above* those listed above are safe.

- Download latest Firefox
- Download latest Thunderbird

You can learn more about this vulnerability and see the official advisories here

- Mozilla Foundation Security Advisory 2022-02
- CVE Details on CVE-2022-22751

Mozilla often rewards researchers for finding these bugs through their bug bounty program, showing their commitment to browser security.

Summary

- CVE-2022-22751 is a grab-bag of memory safety bugs in Firefox 95 and below, Firefox ESR 91.4 and below, and Thunderbird 91.4 and below.
- These bugs could be used by hackers to run malicious code just by getting you to visit a website or read an email.

Stay informed by checking security advisories regularly.

Remember, keeping your software up-to-date is the single best step you can take to protect yourself online!

Timeline

Published on: 12/22/2022 20:15:00 UTC
Last modified on: 12/29/2022 22:55:00 UTC