CVE-2022-22753 - Time-of-Check Time-of-Use Bug in Maintenance (Updater) Service Allows Privilege Escalation in Firefox for Windows

Hello All,

In this post, we will discuss CVE-2022-22753, a Time-of-Check Time-of-Use (TOCTTOU) bug in the Maintenance (Updater) Service of Firefox, which can be exploited to grant Windows users write access to an arbitrary directory. This vulnerability can lead to system access escalation.

Please note that this bug only affects Firefox on Windows systems. Users running Firefox on other operating systems can rest easy.

Vulnerability Details

A TOCTTOU bug was discovered in the Maintenance (Updater) Service of Firefox on Windows. The updater allowed some users, who should not have write access, to manipulate arbitrary directories on the system. This could have led to unauthorized access and, potentially, escalation to SYSTEM access.

To understand this vulnerability better, let's look at a code snippet from the Maintenance (Updater) Service:

// check if user has write access
if (!HasWriteAccess(user_path)) {
    return ERROR_ACCESS_DENIED;
}

// perform update operation (TOCTTOU timing issue)
UpdateDirectory(user_path);

// actual write operation
WriteToFile(user_path, data);

In the code above, the HasWriteAccess function checks if the user has write permissions on a specific path (user_path). If the user does not have write access, the function returns an ERROR_ACCESS_DENIED message. However, there is a Time-of-Check Time-of-Use issue that occurs between the check for write access (HasWriteAccess) and the update operation (UpdateDirectory).

This TOCTTOU timing issue allows a malicious user to manipulate the user_path between the access check and the update operation. This grants write access to an arbitrary directory, which could then be exploited to escalate to SYSTEM access.

For more information about this vulnerability, please consult the following resources

- Mozilla Security Advisory
- Mozilla Foundation Security Vulnerability Description
- CVE-2022-22753 - NIST National Vulnerability Database

Remediation

To protect against exploitation of this vulnerability, users should make sure that they are using the most recent versions of Firefox, Thunderbird, and Firefox ESR. Update to:

Firefox ESR 91.6. or later

Staying up-to-date with the latest software patches and updates is the best way to keep your system secure and protect yourself from security threats like CVE-2022-22753.

Feel free to share your thoughts or ask any questions regarding this vulnerability in the comments below. Stay safe and secure your systems!

Timeline

Published on: 12/22/2022 20:15:00 UTC
Last modified on: 12/29/2022 23:03:00 UTC