macOS is famous for its security, but even Apple products aren’t invincible. One of the more interesting vulnerabilities discovered in recent years is CVE-2022-42791. This bug was patched in macOS Ventura 13, but before the fix, it exposed millions of users to potential kernel-level code execution—a nightmarish thought for any Mac owner! In this post, we’ll unpack what went wrong, see some example code, and dig into the details of the exploit.

What is CVE-2022-42791?

CVE-2022-42791 is a security flaw involving a race condition in the macOS kernel. A race condition happens when two or more processes try to change or access the same data at the same time, resulting in unpredictable and unsafe behavior.

With CVE-2022-42791, a malicious app could exploit this race condition to execute arbitrary code at the kernel privilege level. In simple terms: an app could become the most powerful user on your Mac — bypassing all built-in protections.

Where to Read More

- Apple’s Security Update Details for Ventura 13
- National Vulnerability Database Entry
- Mitre CVE Details

The Technical Root: Race Condition in the Kernel

The issue lived in how the macOS kernel handled certain system calls, particularly involving state management of kernel objects. If two threads hit a critical section of code at just the right time, the kernel’s internal state could become corrupted. This opens a small window for an attacker to inject their own code into the kernel’s memory space.

Here’s a Digested Example (Pseudocode)

Let's imagine a kernel object (e.g., mystruct). Normally, access to mystruct needs to be strictly managed. But before the patch, the code might have looked like this:

// Pseudo C-like code for illustration only
void handle_request(struct mystruct *obj) {
    if (!obj->is_initialized) {
        initialize(obj);
        obj->is_initialized = true;
    }
    use(obj); // Potentially unsafe if another thread initializes at the same time
}

If a malicious app could trigger two threads to run handle_request() at the same time on the same obj, one might use an uninitialized object or overwrite it unexpectedly. If carefully timed, this could let the attacker control object values—and possibly hijack the kernel’s execution flow.

Let’s break down what a potential exploit scenario might look like

1. Trigger the Race: The attacker creates multiple threads performing specific kernel calls targeting the vulnerable code, all at once.
2. Corrupt State: With the right timing, the internal state of a kernel object gets corrupted. For example, a “not fully initialized” object might suddenly be accessed by another thread.
3. Hijack Execution: By carefully crafting object fields, an attacker can trick the kernel into running their own code with root (kernel) privileges.

A proof-of-concept (PoC) could look like this (purely illustrative)

#include <pthread.h>
#include <kernel_api.h> // Not real; for demonstration

struct mystruct *shared_obj;

void *thread_func(void *arg) {
    while (1) {
        handle_request(shared_obj);
    }
    return NULL;
}

int main() {
    pthread_t t1, t2;
    shared_obj = get_kernel_object();

    pthread_create(&t1, NULL, thread_func, NULL);
    pthread_create(&t2, NULL, thread_func, NULL);

    pthread_join(t1, NULL);
    pthread_join(t2, NULL);

    return ;
}

By running both threads simultaneously, a hacker tries to hit the “race window”, causing the kernel to mishandle memory or function pointers.

The Official Fix

Apple’s engineers fixed the bug with “improved state handling.” This usually means introducing proper synchronization mechanisms (like locks or atomic operations) to protect the kernel’s internal data. Now, once a thread starts to initialize or use obj, others must wait their turn. No more dangerous overlapping.

You can see in the official release notes

> A race condition was addressed with improved state handling. This issue is fixed in macOS Ventura 13. An app may be able to execute arbitrary code with kernel privileges. — Apple Support Article

Kernel Access = Complete System Control

Exploitation would let malware or a rogue app break out of its sandbox, disable security tools, steal data, or brick the operating system.

Staying Protected

Update your Mac!  
If you’re using anything before macOS Ventura 13, you’re at risk. Go to Apple Menu > System Settings > General > Software Update and make sure you’re fully patched.

Conclusion

CVE-2022-42791 is a textbook example of how small coding mistakes like race conditions can have massive security consequences. Apple’s fast response and improved state handling in Ventura 13 closed this dangerous door. For users, updates are your best friend. For developers, it’s a reminder: guard your critical sections with care — attackers only need milliseconds.

- Apple Security Updates
- NVD Entry for CVE-2022-42791
- Mitre CVE Details


Stay safe, and always keep your systems up-to-date!

Timeline

Published on: 11/01/2022 20:15:00 UTC
Last modified on: 11/10/2022 04:15:00 UTC