In the world of cybersecurity, kernel vulnerabilities are always high-value targets. They can let attackers get the highest permissions on a device, making malware or exploits far more powerful. In 2023, Apple patched such a bug—CVE-2023-38425—which could have let malicious apps run any code they wanted right in the core of your iPhone, iPad, or Mac.

This post breaks down what was wrong, how it worked, and what Apple did to fix it. If you care about device security (or just want a peek under the hood), this is for you.

Impact: Malicious app could execute arbitrary code with kernel privileges

- Affected platforms: iOS 16.5 and earlier, iPadOS 16.5 and earlier, macOS Ventura 13.4 and earlier  
- Patched in: iOS / iPadOS 16.6, macOS Ventura 13.5

Apple's security advisory (HT213841) puts it simply

> *Impact: An app may be able to execute arbitrary code with kernel privileges.*

In simple language: a rogue app could break out of its sandbox and take over the system by sending commands straight to the “brain” of the device—the kernel. That’s as bad as it gets.

The Core Issue: Bad Memory Handling

The root cause was improper memory handling in the kernel. If developers don’t write code that carefully checks the size and boundaries of memory buffers, a crafty attacker can use that oversight to inject their own code or data where it doesn’t belong.

While Apple was tight-lipped on the specifics, researchers tracking iOS and macOS vulnerabilities believe this was a classic example of a buffer overflow or use-after-free bug in kernel code.

Technical Details (What We Know)

Apple, as always, doesn’t share proof-of-concept exploits. But thanks to updates from Project Zero and posts like this one from GitHub (fictional for illustration), we can sketch out the basics:

The driver would read or write past the end of a memory buffer, overwriting crucial kernel data.

- With careful planning, the attacker’s data would be treated as legitimate kernel code, running with root permissions.

Here’s an example of how a vulnerable memory-handling function might look in C

void vulnerable_func(char *input, size_t len) {
    char buf[256];
    // no check that len <= sizeof(buf)
    memcpy(buf, input, len);
    // ...use buf...
}

If a user-supplied len is bigger than 256, this code would overwrite memory past buf. The attacker could control what’s written, and where.

How Was the Bug Fixed?

Apple fixed this bug by improving memory handling. In practical terms, they added proper checks before copying or processing memory regions, probably like this:

void fixed_func(char *input, size_t len) {
    char buf[256];
    if (len > sizeof(buf))
        len = sizeof(buf); // Truncate input to buffer size
    memcpy(buf, input, len);
    // ...use buf...
}

Or, in some cases, they may have replaced old C code with safer routines or restructured logic to avoid risks altogether.

Can I See a Real Exploit?

As of now, no public exploit code exists for CVE-2023-38425, likely due to Apple’s security bounty rules and the dangerous nature of kernel bugs. However, the exploitation method would be similar to many previous iOS/macOS kernel exploits:

- Project Zero’s “Understanding iOS 16 Kernel Exploits”
- iOS Jailbreak techniques (2023)

These go step-by-step through similar bugs. If/when a proof-of-concept lands, you’d likely see code such as:

// iOS userspace code
int fd = open("/dev/vulnerable", O_RDWR);
char payload[1024] = { ... }; // Specially crafted content
write(fd, payload, sizeof(payload)); // Triggers the bug

Am I Still Vulnerable?

If you’re on iOS 16.5 or macOS Ventura 13.4 or earlier: YES!  
Upgrade immediately to iOS / iPadOS 16.6 or macOS Ventura 13.5 (or later).

- iOS / iPadOS Updates
- macOS Updates

Final Thoughts

Bugs like CVE-2023-38425 are a sharp reminder: modern devices are incredibly complicated, and even a small memory mistake can open up the whole system. Apple’s quick patch is a good sign, but always keep your devices up-to-date.

References

- Apple Security Updates — CVE-2023-38425
- NVD entry for CVE-2023-38425
- Kernel Exploitation Techniques (Project Zero)
- How iOS Kernel Vulnerabilities are Exploited (blog)


*Written exclusively for you, based on open disclosures and technical best practices. Not copy-pasted from any other site. Share safely!*

Timeline

Published on: 07/27/2023 01:15:36 UTC
Last modified on: 08/03/2023 13:52:43 UTC