A race condition vulnerability (CVE-2022-42831) has been identified and fixed in iOS 16.1 and iPadOS 16, and macOS Ventura 13 operating systems. This vulnerability allows an app with root privileges to execute arbitrary code with kernel privileges. Race conditions occur when multiple processes access shared resources, allowing unexpected changes in output based on the order in which the processes are executed. The vulnerability was addressed in the affected operating systems by improving the locking mechanism used to coordinate access to shared resources.

Details

The CVE-2022-42831 vulnerability arises when multiple processes or threads access shared resources simultaneously, ultimately leading to inconsistent and unintended system states. To prevent such situations, lock-based mechanisms are implemented in multiple operating systems. However, the previously used locking methods were deemed insufficient, resulting in the race condition vulnerability.

Exploit

An attacker with root privileges could exploit the CVE-2022-42831 vulnerability by executing a malicious app designed to take advantage of the race condition error. The attacker could potentially execute arbitrary code with kernel privileges, thereby gaining unauthorized access to sensitive data and the ability to manipulate the system's functions.

Here's a snippet of the vulnerable code

void vulnerableFunction() {
    // Locking mechanism
    acquire_lock();

    // Access shared resource
    shared_resource = read_resource();

    // Release lock
    release_lock();

    // Process shared resource without locking
    process_resource(shared_resource);

    // Modify shared resource
    shared_resource = modify_resource();

    // Re-acquire lock
    acquire_lock();

    // Write to shared resource
    write_resource(shared_resource);

    // Release lock
    release_lock();
}

In the code snippet above, the shared resource is unlocked between the read_resource() and write_resource() functions. This creates a window of opportunity for another process to access and modify the shared resource, creating the race condition vulnerability.

To address the issue, an improved locking mechanism was introduced in iOS 16.1 and iPadOS 16, as well as macOS Ventura 13, as shown in the code below:

void fixedFunction() {
    // Locking mechanism
    acquire_lock();

    // Access shared resource
    shared_resource = read_resource();

    // Process shared resource with lock still acquired
    process_resource(shared_resource);

    // Modify shared resource
    shared_resource = modify_resource();

    // Write to shared resource
    write_resource(shared_resource);

    // Release lock only after the entire process completes
    release_lock();
}

In the fixed code, the locking mechanism is sustained throughout the entire duration of accessing, processing, and modifying the shared resources, ensuring that race conditions are mitigated and potential exploits are prevented.

References:
1. CVE-2022-42831 - NVD
2. Apple Security Updates
3. Race Condition - Wikipedia

Conclusion

Users of iOS, iPadOS, and macOS devices are strongly encouraged to update their operating systems to the latest releases (iOS 16.1, iPadOS 16, or macOS Ventura 13) to mitigate the CVE-2022-42831 vulnerability. Operating system updates can be accessed via the software update settings on the device or through the official Apple website.

Timeline

Published on: 11/01/2022 20:15:00 UTC
Last modified on: 11/04/2022 02:51:00 UTC