Apple products are known for their strong system security. But no system is fully bulletproof. In 2022, researchers found a critical vulnerability, CVE-2022-42803, that opened the door for attackers to run code at the heart of macOS, iOS, iPadOS, tvOS, and watchOS. Let’s break down what this bug was, how it could be exploited, and how Apple fixed it.

What’s CVE-2022-42803?

CVE-2022-42803 is a race condition in the operating system kernel of Apple products. A race condition is a bug that happens when a system's outcome depends on the timing or sequence of events. If an attacker knows how to manipulate timing, they can exploit this unpredictably.

In this case, the flaw could let a rogue app run code with kernel privileges—the highest level of access—to essentially control the whole device.

Devices Affected

- iPhones/iPads: iOS 15.7.1 & iPadOS 15.7.1, iOS 16., iPadOS 16.

Hide from antivirus tools.

A bug like this is often used in jailbreaks or sophisticated spyware.

Technical Details: The Race Condition

Apple did not share much about the exact code, but according to the security release notes, the flaw resided in the kernel, the core part of an operating system. When multiple processes accessed shared kernel memory at the same time, the system didn’t properly lock these resources. This allowed the state of the system to change between checks, leading to unpredictable (and exploitable) behavior.

The vulnerability’s root cause is called a Time-of-Check to Time-of-Use (TOCTOU) bug. Let’s look at a simplified code example to understand:

// Simplified example of a TOCTOU bug

if (check_permissions(user)) {
    // Attacker can race here and change user data!
    access_secure_resource(user);
}


If the attacker can change the user object between the permission check and the resource access, they might gain unauthorized privilege.

Disclaimer: For educational purposes only.

Imagine a malicious app on iOS sends many threads to the kernel, all trying to access a sensitive function at the same time, racing to change a value between different checks.

A basic pseudocode exploit could look like this

// Pseudocode; not functional

while (!got_access) {
    thread1: change_shared_value_to_attack();
    thread2: trigger_kernel_api_with_changed_value();
    // The goal: win the race condition!
    if (kernel_returns_success()) {
        got_access = true;
        escalate_privileges();
    }
}

In practice: Real-world exploitation is complex and needs deep kernel knowledge. Attackers might use special APIs exposed to apps and then synchronize multiple threads to control timing, hoping to “win” the race and execute code in kernel mode.

How Apple Fixed It

The Apple fix is described as “improved locking” (HT213489). That means Apple added mutexes or other synchronization tools to make sure only one process can access or change the sensitive data at a time.

A simplified fix might look like

// Secure code example

lock(mutex);
if (check_permissions(user)) {
    access_secure_resource(user);
}
unlock(mutex);

Now, the attacker can’t change the state between those two actions.

iOS 16.1 and iPadOS 16

Reference:  
- Apple Security Updates  
- HT213489: About the security content of iOS 15.7.1 and iPadOS 15.7.1

Limit app installs: Stick to official sources.

- Don’t jailbreak: Jailbreaking makes it much easier for malware to exploit these kinds of flaws.

This race condition is a reminder—even in the best systems, simple mistakes like missing a lock can have severe consequences.

References

- CVE-2022-42803 on MITRE  
- Apple Security Updates  
- Apple’s Patch Notes for iOS 15.7.1


In summary: CVE-2022-42803 is a serious bug, now fixed, that could have let apps take over Apple devices by exploiting a race condition in the kernel. If you want to keep your Apple devices safe, update early and update often!

Timeline

Published on: 11/01/2022 20:15:00 UTC
Last modified on: 11/03/2022 03:53:00 UTC