A new vulnerability, CVE-2023-28162, has been identified in Firefox, Firefox ESR, and Thunderbird, which could lead to a potentially exploitable crash. This vulnerability arises from improper type casting in the implementation of AudioWorklets. In this post, we'll dive into the details of this vulnerability, its exploitation, and possible mitigations. We'll also provide code snippets and links to the original references for better understanding.

Background

AudioWorklets are a part of the Web Audio API, designed to allow developers to process and synthesize audio directly in the browser using JavaScript. AudioWorklets are particularly useful for implementing custom audio effects, such as a virtual guitar pedalboard, or visualizations, like a real-time frequency analyzer.

Vulnerability Details

In the vulnerable versions of Firefox and Thunderbird, some code responsible for implementing AudioWorklets may have casted one type to another, invalid, dynamic type. This improper type casting could lead to memory corruption or other undefined behavior that could result in a potentially exploitable crash.

The following code snippet demonstrates how the vulnerable type casting could occur

class VulnerableAudioWorklet extends AudioWorkletProcessor {
  process(inputs, outputs, parameters) {
    const input = inputs[];
    const output = outputs[];

    // Cast Float32Array to an invalid dynamic type
    const castedInput = new Uint8Array(input.buffer);

    for (let i = ; i < input.length; i++) {
      output[][i] = castedInput[i];
    }

    return true;
  }
}

registerProcessor('vulnerable-audio-worklet', VulnerableAudioWorklet);

References to the original vulnerability disclosure and patch can be found here

- Mozilla Security Advisory
- Bugzilla Report
- GitHub Patch

Exploitation

An attacker could exploit CVE-2023-28162 by crafting a malicious website that employs the vulnerable AudioWorklet implementation. When a user visits this website using an unpatched version of Firefox or Thunderbird, the improper type casting would trigger the exploitable crash. This crash could potentially allow the attacker to execute arbitrary code, steal sensitive information, or perform other malicious actions on the user's machine.

Mitigation

The best way to mitigate this vulnerability is to update to the latest, patched version of Firefox, Firefox ESR, or Thunderbird:

Update to Thunderbird 102.9 or later

These updates can be obtained from the official Mozilla website.

Conclusion

CVE-2023-28162 is a critical vulnerability in Firefox, Firefox ESR, and Thunderbird's implementation of AudioWorklets. Users of these software should update to the latest versions as soon as possible to mitigate the risk of exploitation. Developers working with AudioWorklets should be cautious of potential type casting issues and ensure that proper validation and type checking is implemented to prevent similar vulnerabilities in the future.

Timeline

Published on: 06/02/2023 17:15:00 UTC
Last modified on: 06/09/2023 17:03:00 UTC