Introduction: Cross-origin information leaks through Web Workers

In recent years, web technologies have significantly improved, with developers increasingly relying on powerful tools such as Web Workers to optimize the performance of their applications. However, these advancements may also bring potential security risks, as shown by vulnerability CVE-2022-22760. This vulnerability, which affects Mozilla's Firefox, Thunderbird, and Firefox ESR, exposes sensitive cross-origin information due to a peculiarity in error messages generated by Web Workers.

This comprehensive post will delve into the details of CVE-2022-22760, including its root cause, the code snippet that demonstrates the vulnerability, links to original references, and mitigation strategies for affected users.

The CVE-2022-22760 vulnerability: Error messages reveal cross-origin information

The core issue in CVE-2022-22760 lies within the error messages generated by Web Workers when importing resources. Specifically, these error messages expose the difference between application/javascript responses and non-script responses, which could be abused by attackers to gather sensitive cross-origin information.

Affected software versions include Firefox (prior to version 97), Thunderbird (prior to version 91.6), and Firefox ESR (prior to version 91.6).

A code snippet illustrating the vulnerability

Suppose an attacker seeks to exploit this vulnerability in a web application that uses Web Workers to import resources. The malicious party could attempt to run the following JavaScript code snippet:

// Create a new Web Worker instance
const worker = new Worker('worker-script.js');

// Listen for error messages from the Web Worker import
worker.onerror = function (event) {
  if (event.message.indexOf('application/javascript') !== -1) {
    console.log('Resource is a script');
  } else {
    console.log('Resource is not a script');
  }
};

// Import the target resource
worker.postMessage({action: 'importResource', url: 'https://target-website.com/resource';});

This code example would generate error messages differentiating between script and non-script resources, potentially revealing sensitive cross-origin information.

Original references

1. Mozilla Foundation Security Advisory 2022-08
2. Mozilla Foundation Security Advisory 2022-09
3. Mozilla Foundation Security Advisory 2022-10
4. CVE Details Page for CVE-2022-22760

Mitigating the CVE-2022-22760 vulnerability

Users of Mozilla's Firefox, Thunderbird, and Firefox ESR can implement the following measures to mitigate the CVE-2022-22760 vulnerability:

1. Update your software: The most effective solution is to update affected software versions to their latest releases, which already contain security fixes for CVE-2022-22760. Firefox users should update to version 97 or later, while Thunderbird and Firefox ESR users should update to version 91.6 or later.

2. Be cautious with cross-origin resource sharing (CORS): Web developers should exercise caution when configuring CORS policies for their web applications, ensuring that they do not enable untrusted origins to access sensitive information.

3. Employ content security policies (CSP): A strict CSP can help protect web applications from cross-origin information leaks. Developers can use CSP to restrict the sources of scripts, styles, and other assets, thereby mitigating potential vulnerabilities.

Conclusion

In summary, the CVE-2022-22760 vulnerability highlights the potential risks of using Web Workers in web applications. By understanding the nature of this vulnerability, users and developers can take appropriate steps to secure their software and protect sensitive information from being compromised. As browsers and web technologies continue to evolve, it is essential for the security community to remain vigilant, identifying and addressing vulnerabilities like CVE-2022-22760 to safeguard the internet's continuing growth and innovation.

Timeline

Published on: 12/22/2022 20:15:00 UTC
Last modified on: 12/30/2022 14:03:00 UTC