In the rapidly changing world of cybersecurity, even the biggest players like Apple are not immune to serious bugs. In this post, we’ll break down CVE-2023-38598 — a critical use-after-free vulnerability that was patched in Apple’s Summer 2023 updates. We’ll walk through what a use-after-free bug is, which products and versions were affected, how an attacker could exploit it to run code as root (kernel privileges!), and why your Apple devices should be updated ASAP.

Links to Apple’s official advisories are included, plus simplified technical code snippets illustrating the bug and a peek at potential exploitation.

What Is CVE-2023-38598?

CVE-2023-38598 is a "use-after-free" vulnerability in Apple’s kernel, which if exploited, would let a malicious app run code with the highest privileges — meaning it could pretty much take control of your device. The bug is especially severe because it lives in the core of the OS and impacts several Apple operating systems.

tvOS before 16.6

Apple’s summary:  
>A use-after-free issue was addressed with improved memory management. This issue is fixed in watchOS 9.6, macOS Big Sur 11.7.9, iOS 15.7.8 and iPadOS 15.7.8, macOS Monterey 12.6.8, tvOS 16.6, iOS 16.6 and iPadOS 16.6, macOS Ventura 13.5. An app may be able to execute arbitrary code with kernel privileges. (Apple advisory)

Breaking Down "Use-After-Free"

"Use-after-free" is a type of bug that happens when a program continues to use memory after it’s already been marked as free. When that freed memory gets reused in an unpredictable way, it could let bad actors trick the system into running harmful code.

Simple Metaphor

Imagine renting an apartment (allocating memory). When you move out and hand in the keys (freeing memory), but someone else finds a way in using your old key (dangling pointer). Now, they can do anything inside.

Here’s a simplified illustration

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

int main() {
    int* data = malloc(sizeof(int));
    *data = 42;
    free(data);
    printf("Value: %d\n", *data); // Use-After-Free!
    return ;
}


In this example, the program tries to use memory that’s already freed. Attackers can exploit this kind of logic at a much deeper level — like inside the kernel.

Kernel Privilege Escalation — Why It’s So Dangerous

The Apple kernel is the heart of all macOS, iOS, iPadOS, and tvOS devices. An app exploiting this bug doesn’t just break out of the sandbox — it can gain full control (read/write arbitrary memory, disable security features, etc). Malware can go undetected, rootkits can be installed, and your privacy is gone.

Who could exploit it?

Possible Exploitation Flow

*While Apple doesn’t release proof-of-concept code, based on Apple’s description and public reports, here’s what likely happened:*

1. Trigger the use-after-free: The attacker finds a way to free a memory object (via a kernel API), but still retains a reference to it.
2. Reallocate memory: The attacker fills the now-freed memory space with their own data (sometimes called “heap spraying”).
3. Hijack program execution: When the kernel accesses the stale pointer, it now processes attacker-controlled data, possibly running attacker code with kernel rights.

Pseudocode Exploit Skeleton

// THIS IS A SIMPLIFIED/PSEUDO EXAMPLE, FOR EDUCATIONAL PURPOSES ONLY

void exploit_vuln() {
    void* target = kernel_allocate(); // get resource in kernel
    kernel_use(target); // use it
    kernel_free(target); // free it - bug: still referenced

    heap_spray(attacker_payload); // fill freed area w/ malicious data

    trigger_use(target); // kernel uses attacker data with root permissions!
}

(Actual kernel exploits are much more complex, but this is the core idea.)

The Fix: Improved Memory Management

Apple’s patch changed how memory is tracked and freed in the kernel, ensuring there are no references left after freeing. Any code path that could accidentally use stale pointers was audited and corrected.

What should you do?

Update ALL devices (see versions above)!

- Don’t run untrusted apps, and be wary of suspicious links/messages

References

- Apple Security Advisory (August 2023)
- Apple Security Update For macOS Big Sur 11.7.9
- NIST NVD entry for CVE-2023-38598

Conclusion

CVE-2023-38598 is a scary reminder that low-level bugs can open the door to major attacks, even in devices designed with security in mind. Always be vigilant and keep your software up to date — it’s your first and most important safety net.

Stay safe, keep learning, and remember: even small bugs can have big impacts!

Timeline

Published on: 07/28/2023 05:15:10 UTC
Last modified on: 08/03/2023 16:53:51 UTC