Apple products are known for their tight security, but sometimes, even the strongest walls have cracks. In 2022, a critical vulnerability was discovered in the Apple kernel that had the potential to let apps execute arbitrary code with the highest privileges (!). In this article, we’ll take a closer look at CVE-2022-32903, explain how it works, show you some code snippets, and summarize what security teams need to know to protect users.

What is CVE-2022-32903?

CVE-2022-32903 is a "use-after-free" bug. In plain English, it means that the system accidentally uses memory that has already been released or “freed.”
This can open the door for attackers to slip in and run their own code at deep system levels, giving them full control over the device—yikes!

The Apple security notes describe it as

> "A use after free issue was addressed with improved memory management. An app may be able to execute arbitrary code with kernel privileges."

Apple's security note:
- https://support.apple.com/en-us/HT213445

What is “Use-After-Free”?

Think of your phone’s memory as a set of boxes. When you’re done using a box, you return it. But what if you put new stuff in that box and someone else sneaks in and swaps it for something dangerous? That’s the risk with “use-after-free.”

The Vulnerable Code (Simplified Example)

While Apple hasn’t released the exact vulnerable code, many Use-After-Free bugs look similar. Let’s imagine a kernel function that manages objects like this:

void vulnerable_function(Object *obj) {
    free(obj);   // The object is released from memory
    // ...
    obj->data = 42;  // Oops! We're still using the object
}

What’s wrong here?
After free(obj), the object “obj” shouldn’t be touched! But the old code keeps using it.

If an attacker can control timing, they might *allocate* something new during the gap—placing their own data where obj used to be. Now, when the code writes to obj->data, it actually modifies attacker-controlled memory. This could lead to arbitrary code execution.

Realistic Kernel Exploit Flow

1. Trigger use-after-free: Craft operations via a custom app that cause the kernel to free a target object but keeps a pointer to it.
2. Reclaim freed memory: Spray the kernel heap with attacker-controlled memory where the freed object was.
3. Hijack execution: When the kernel later reuses the pointer, it acts on attacker data, possibly causing it to execute malicious code with kernel privileges.

Below is a highly simplified sketch of a userland use-after-free (for education)

#include <stdio.h>
#include <stdlib.h>

typedef struct {
    int (*fn)(void);
} Object;

int attacker_function(void) {
    printf("Arbitrary code execution!\\n");
    return ;
}

int main() {
    Object *obj = malloc(sizeof(Object));
    obj->fn = NULL;
    free(obj);  // Object is freed

    // Attacker: Reallocate and overwrite freed memory
    Object *evil = malloc(sizeof(Object));
    evil->fn = attacker_function;

    // Use-after-free: Still using old pointer
    obj->fn();  // Calls attacker_function, simulating kernel code execution

    free(evil);
    return ;
}

Note: In real life, this happens with *kernel* objects, not user apps, and is much more complex.

Apple Security Update for iOS 16:

https://support.apple.com/en-us/HT213445

Apple Security Update for tvOS 16:

https://support.apple.com/en-us/HT213446

Apple Security Update for watchOS 9:

https://support.apple.com/en-us/HT213447

MITRE CVE entry:

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-32903

Who is at Risk?

If you have an iPhone, iPad, Apple TV, or Apple Watch from *before* September 2022 — and you haven’t updated — you could be vulnerable.

Fix and Recommendations

Apple addressed this issue by improving how memory is managed and making sure freed objects aren’t accessed by mistake.

How to protect yourself:

Summary

CVE-2022-32903 is a textbook example of why memory management is so important in system software. With a little race condition and opportunity, attackers can go from sandboxed apps to kernel-level control. The good news: Apple fixed it, and users who update are safe!

Stay safe, stay updated!

If you're interested in kernel security or want to learn more about use-after-free bugs, here are some good starting points:

- Google Project Zero: Exploiting Use-After-Free Vulnerabilities
- OWASP: Use-after-free


Did you find this helpful? Let us know if you want deep dives on iOS security or want more code example tutorials!

Timeline

Published on: 11/01/2022 20:15:00 UTC
Last modified on: 11/02/2022 16:04:00 UTC