CVE-2022-22737: Exploring the Race Condition and Use-After-Free Vulnerability in Firefox and Thunderbird Audio Sinks

CVE-2022-22737 refers to a significant security vulnerability discovered in popular web browsers Firefox and Thunderbird. This vulnerability is a combination of a race condition and a use-after-free issue, which could potentially cause a crash, thereby making systems running these programs exploitable. This post delves into the details of this vulnerability by examining the code snippets, offering links to original references, and discussing exploit possibilities. The affected versions include Firefox ESR < 91.5, Firefox < 96, and Thunderbird < 91.5, and the following content discusses crucial aspects of the vulnerability.

Code Snippet

The vulnerability lies in the process of constructing audio sinks during audio playback. The issue arises when a race condition occurs simultaneously while playing audio files and closing windows.

The potential problematic code snippet in Firefox and Thunderbird may look like this

void AudioSink::Run() {
  ...
  while (!mDone) {
    int64_t audioDuration();
    {
      MonitorAutoLock mon(mMonitor);
      ...
      audioDuration = ...;
    }
    if (audioDuration && !HasAudio()) {
      ...
      mAudioStream->SetPlaying(true);
      ...
    }
    ...
  }
  ...
}

The mDone variable, when set to true, signals that the Run function should exit before releasing the resources for the audio sink. However, under specific conditions (e.g., quickly closing a window during the audio playback), mDone may not be set appropriately which may lead to a use-after-free when the destructor for the audio sink is called.

Original References

This vulnerability was initially discovered and reported by a security researcher. The official advisory and details regarding the vulnerability can be found in the following sources:

1. Mozilla Foundation Security Advisory: MFSA 2022-05
2. National Vulnerability Database: NVD - CVE-2022-22737

Exploit Details

This use-after-free vulnerability, in combination with a race condition, could potentially lead to a crash and make a system running an unpatched version of Firefox or Thunderbird exploitable. An attacker could use this vulnerability in a variety of ways, including:

1. Crafting a malicious web page that, when visited with an unpatched Firefox, triggers the race condition and the use-after-free vulnerability, ultimately causing the browser to crash and potentially allowing the attacker to execute arbitrary code on the victim's system.
2. Sending a malicious email with a crafted audio attachment, tricking the recipient into playing the audio file in Thunderbird, and once again, triggering the race condition and use-after-free vulnerability.

Conclusion

CVE-2022-22737 serves as a reminder of the importance of keeping our software up to date and the need to be vigilant when browsing the internet or opening email attachments. Users should ensure they have applied the necessary updates to their Firefox and Thunderbird installations to mitigate this vulnerability. The affected versions Firefox ESR < 91.5, Firefox < 96, and Thunderbird < 91.5 should be updated to the patch. Protecting ourselves from potential exploits rests in our hands, and staying informed and prepared is the key to a safe online experience.

Timeline

Published on: 12/22/2022 20:15:00 UTC
Last modified on: 12/29/2022 15:50:00 UTC