In early 2022, Apple patched a severe security flaw labeled CVE-2022-22640. This vulnerability let malicious apps gain kernel-level privileges by exploiting a memory corruption issue. This post gives an exclusive, easy-to-read background, a look at how the bug works, how it was fixed, and why it mattered so much.

What Is CVE-2022-22640?

CVE-2022-22640 is a memory corruption vulnerability found in the AppleAVD component, which is Apple's framework for video decoding. The issue was found in Apple devices running:

tvOS (before 15.4)

- iOS/iPadOS (before 15.4)

Apple described the issue simply

> An application may be able to execute arbitrary code with kernel privileges. A memory corruption issue was addressed with improved validation.

In plain terms: a bad app could ruin protected memory and trick the system into running hacker code as if it was the most trusted system code.

Official advisory:

Why Is This So Dangerous?

The kernel is the heart of any operating system. If you can run code as the kernel, you have full control: you can read files, change system settings, and even wipe everything. That's why kernel vulnerabilities are extremely valuable and dangerous.

This bug didn't require physical access or advanced user tricks — just a malicious app.

How Did the Bug Happen?

The root cause was a lack of strong checks in AppleAVD during memory operations. For the technical folks:

Attackers could cause heap or stack memory corruption.

By sending specially crafted input, an attacker could overwrite important memory sections.

Below is a simplified C pseudo-code (not the actual code) to show what went wrong

// Hypothetical vulnerable function in AppleAVD
int handle_input_from_app(void *user_buffer, size_t length) {
    char kernel_buffer[256];

    // BAD: No check if length is too big for the buffer
    memcpy(kernel_buffer, user_buffer, length);

    // ... process kernel_buffer ...
    return ;
}

If an attacker sends a length bigger than 256, they overwrite adjacent kernel memory. By carefully crafting the data, they can hijack code execution.

Get the kernel to execute their custom code, gaining total control.

This can escalate to jailbreaks, malware, or full device takeovers.

Here's a skeleton exploit (for research/education, NOT to use!)

// Open AppleAVD device
int fd = open("/dev/apple_avd", O_RDWR);

// Craft oversized buffer
char evil_buf[4096];
memset(evil_buf, 'A', sizeof(evil_buf));

// Send it via IOCTL or write
write(fd, evil_buf, sizeof(evil_buf));

// Close
close(fd);

*Note: The real exploit is much more complex, but this shows the basic idea.*

Patched AppleAVD driver in all affected operating systems.

Update notes:
- Apple security updates, March 2022
- Apple iOS 15.4 release notes

Likely not, if you have updated to

- iOS/iPadOS 15.4 or newer

Further Reading

- CVE-2022-22640 at NIST
- Apple’s official advisory for CVE-2022-22640

Summary

CVE-2022-22640 was a serious kernel-level memory bug in Apple devices, letting attackers run their own code with the highest system privileges. Apple’s fix was relatively simple — but as always, these vulnerabilities teach us how critical it is to check *every* input, *every* time, especially deep in the system.

Stay safe: Update your Apple devices, and be mindful of what you install.

Did you enjoy this deep-dive? Let us know if you want more easy-to-read breakdowns of real-world security bugs!

Timeline

Published on: 03/18/2022 18:15:00 UTC
Last modified on: 03/24/2022 18:39:00 UTC