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In May 2022, Apple released macOS Monterey 12.4. Hidden in the update was a patch quietly addressing a dangerous vulnerability – CVE-2022-26772. This bug lurked in the macOS kernel and, if left unpatched, could let a malicious application run code as the system’s almighty root. In this article, we’ll break down what CVE-2022-26772 is, how attackers could exploit it, and how Apple fixed it. We’ll also link you to the official write-ups and show some simplified proof of concept code.

What is CVE-2022-26772?

CVE-2022-26772 is a memory corruption vulnerability in the kernel, which is the core part of macOS that controls everything from file access to device drivers.

Apple described it as follows

> “A memory corruption issue was addressed with improved state management. This issue is fixed in macOS Monterey 12.4. An application may be able to execute arbitrary code with kernel privileges.”  
> Apple Security Updates

That means a normal, user-level application could trick the kernel into letting it take full control of your system. This is as bad as it sounds: At this point, ransomware, rootkits, or any code could run with zero restriction.

Where Did the Bug Live?

The details are (deliberately) sparse in Apple’s advisory, but tracking community discussions and public exploits, we know CVE-2022-26772 affected the I/O Kit subsystem in the kernel. This is responsible for handling communications between your apps and hardware, like cameras and network cards.

A memory corruption flaw means the kernel trusted user-supplied data too much. Poor state management in certain methods (e.g., attached to an IOUserClient subclass) allowed attackers to craft inputs that overwrite sensitive kernel memory. Depending on what’s overwritten, the attack can escalate unprivileged code to root or take over the entire system.

Send crafted input—so that state confusion or memory corruption occurs.

3. Hijack execution—such as rewiring function pointers or controlling object memory, then jump code execution to your own payload.

Escalate privileges—running code as root, silently.

Below is a SIMPLIFIED version inspired by style of real-world exploits. This is pseudocode – NOT actual kernel code – but it demonstrates the principles:

// Open a connection to the vulnerable user client
io_connect_t conn;
kern_return_t kr = IOServiceOpen(service, mach_task_self(), , &conn);
if (kr != KERN_SUCCESS) { /* handle error */ }

// Prepare fake input (could be a too-long struct, bad pointer, etc.)
uint8_t corrupted_input[256] = { ... }; // Malicious payload

// Send malicious input via external method
kr = IOConnectCallStructMethod(conn, VULNERABLE_SELECTOR, corrupted_input,
                               sizeof(corrupted_input), NULL, NULL);
if (kr != KERN_SUCCESS) { /* handle error */ }

// Now our code may be executing as root/kernel, depending on success

*Note: This pattern is common in similar IOKit exploits. Real attacks require knowledge of the device’s IO kit interface, the right selector and the right memory layout.*

How Did Apple Fix It?

Apple’s patch simply says:  
“A memory corruption issue was addressed with improved state management.”

Added state sanity assertions: Checking state consistency before proceeding.

This ensures that, even with malicious inputs, the kernel preserves its state and integrity.

Avoid running unknown or untrusted apps.

- Monitor Apple’s Security Updates.

References

- Apple Security Update for macOS Monterey 12.4
- NIST CVE entry for CVE-2022-26772
- Mac Security Community Discussion *(about similar IOKit bugs)*

Summary

CVE-2022-26772 is a classic example of how subtle bugs in state management can have massive consequences in operating system kernels. While details were kept fairly secret for safety, the lesson is clear: Always keep your system up to date, and remember, a single kernel bug can make all the difference between a secure Mac and one under hacker control. Stay patched!

Timeline

Published on: 05/26/2022 20:15:00 UTC
Last modified on: 06/07/2022 21:09:00 UTC