In July 2023, Apple released updates to patch a serious security vulnerability identified as CVE-2023-38424. This flaw potentially allowed a malicious app to execute arbitrary code with kernel-level privileges, putting the security of iOS, iPadOS, and macOS devices at risk. In this post, we'll break down the vulnerability, summarize Apple's official fix, peek into how exploits might work, and include a sample code snippet to illustrate the kind of error involved.

Severity: High

- Type: Memory handling/kernal privilege escalation
- Resolved in: iOS/iPadOS 16.6, macOS Ventura 13.5

Apple's Official Description

> "The issue was addressed with improved memory handling. This issue is fixed in iOS 16.6 and iPadOS 16.6, macOS Ventura 13.5. An app may be able to execute arbitrary code with kernel privileges."  
> — Apple Security Updates Archive

How Did the Vulnerability Work?

While Apple does not publish full technical details, security researchers and Apple mention that this was a kernel memory handling issue. In simple terms, apps could trick the operating system into letting them write or execute code at the kernel level—the lowest, most powerful level of the system. With kernel privileges, malware could bypass system protections, steal data, or install persistent backdoors.

Simplified Example (C-Style Pseudo Code)

Although we don’t have the exact vulnerable code, here's a classic type of memory bug that could lead to such a flaw:

// pseudo-code representing a memory corruption vulnerability
void vulnerable_function(char *user_input) {
    char buffer[256];
    // Unsafe: no size check before copying
    strcpy(buffer, user_input);  
    // ... later, the buffer is used in a kernel call
}

An attacker could supply more than 256 bytes of input, overwriting important values on the stack—a classic buffer overflow.

In Apple’s case, the vulnerable function would be running in the kernel, and the error would allow writing code that the kernel would then execute, granting full device control.

Malicious App: The attacker convinces the victim to install a seemingly legitimate app.

2. Triggering the Flaw: The app sends specially crafted data to a vulnerable system component, causing memory corruption.
3. Privilege Escalation: The exploit takes control of kernel execution, possibly by redirecting function pointers or overwriting security-critical structures.
4. Impacts: The attacker may gain unrestricted access to the device, install spyware, or evade future detection.

Discovery and Internal Patch: Usually, Apple is tipped off by researchers or their own audits.

- Coordinated Fix: Apple silently fixes the issue in upcoming releases and publicly announces in security notes later.
- Update Required: Users need to update to iOS 16.6/iPadOS 16.6 or macOS Ventura 13.5 to patch the hole.

Real-World Code Footprint

While real exploit code is not available for obvious reasons, here's a simplified exploit skeleton to illustrate the concept:

// ATTACKER'S PSEUDO-EXPLOIT SNIPPET (DO NOT USE ILLEGALLY)
char evil_input[512];
// Fill evil_input with payload that overwrites control structures
memset(evil_input, 'A', 512); 
// Set up shellcode or jump addresses here, depending on vulnerability
...

// Call vulnerable function in the context of the malicious app
vulnerable_function(evil_input);  // Hypothetical kernel call

Note: Real-world exploits for Apple OS require much more sophistication because of hardware protections like PAC, KASLR, and sandboxing.

References

- Apple Security Updates
- Apple Security Release Notes for iOS 16.6
- APPLE-SA-2023-07-24-2 Security Update 2023-07-24
- MITRE CVE Record

How To Stay Safe

- Update Immediately: If you use an affected Apple device, make sure you’re on iOS/iPadOS 16.6 or macOS Ventura 13.5 (or later).

Avoid Unknown Apps: Only install apps from trusted sources.

- Keep System Protections On: Keep Gatekeeper, System Integrity Protection (SIP), and other defenses enabled.

Summary

CVE-2023-38424 was a critical Apple kernel memory handling bug that, if left unpatched, could allow total device compromise. Apple’s fix involved making memory operations in the kernel safer to prevent this kind of privilege escalation. Security vulnerabilities will never go away, but being quick to update is the best defense!

Timeline

Published on: 07/27/2023 01:15:36 UTC
Last modified on: 08/03/2023 13:57:36 UTC