Leveraging AI Assistants for macOS Kernel Exploit Development: A Five-Day Journey with Mythos Preview

Overview

Developing a working macOS kernel exploit on Apple's M5 silicon is no small feat—especially when Apple's security mitigations have been hardening over five years. Yet, a dedicated team recently demonstrated that with the right AI assistant, such a complex task can be accomplished in just five days. This guide walks through how Mythos Preview, an advanced AI coding companion, was used to bypass those protections and achieve the first public kernel memory corruption exploit on M5 Macs. We'll cover the methodology, tools, and key learnings so you can apply similar techniques in your own security research.

Prerequisites

Before diving into the exploit development process, ensure you have the following:

• macOS Development Environment: A Mac running macOS Ventura or newer (preferably on Apple Silicon M3/M4 for testing, though M5 targets are ideal). Xcode 15+ and the latest Command Line Tools.
• Kernel Programming Knowledge: Familiarity with XNU kernel internals, Mach-O binary format, and low-level memory management (pages, zones, etc.).
• Reverse Engineering Skills: Experience with IDA Pro or Ghidra for analyzing kernel binaries.
• Python & C Proficiency: The exploit is built in C for kernel extensions, with Python used for scaffolding and interaction with Mythos.
• Mythos Preview Access: Sign up for Anthropic's Mythos Preview (currently in closed beta). Ensure you have API keys and understand rate limits.
• Security Research Tools: UserFaultLab for reproducing race conditions, and LLDB debugger for kernel debugging.

Step-by-Step Instructions

Step 1: Reconnaissance & Target Selection

Identify a vulnerable kernel extension (kext) or IOKit driver. Use static analysis to find potential memory corruption spots—often in copy-in/copy-out paths or when dealing with user-supplied sizes. In the original exploit, the team focused on a bug in IOSurface that allowed a use-after-free via a race condition. Mythos assisted by suggesting similar CVEs and code patterns from its training data.

Step 2: Setting Up the Interaction with Mythos

Configure Mythos with a system prompt that defines your role as a macOS kernel exploit developer. Example:

You are an expert macOS kernel hacker. Provide concise, working C code for XNU kernel exploits. Include mitigations bypass techniques for Apple Silicon M5. Assume PAC (pointer authentication) and KASLR are enabled.

Use the Mythos API (or web interface) to send queries. For each step, write a detailed description of what you need—e.g., 'Generate a function that triggers a race condition between two threads on an IOSurface object.'

Step 3: Generating Initial Exploit Scaffolding

Ask Mythos to produce a kernel extension skeleton that exposes a user-client interface. The AI might return something like:

// Sample from Mythos (simplified)
IOReturn MyDriverUserClient::externalMethod(uint32_t selector, ...) {
    switch(selector) {
        case kTriggerBug: {
            // Allocate a surface with user-controlled size
            IOSurface *surf = new IOSurface();
            surf->initWithSize(userSize); // potential integer overflow
            break;
        }
    }
}

Review the code carefully—Mythos may introduce logical errors. Modify manually to match the specific kernel version (macOS 14.x for M5).

Step 4: Iterative Refinement via Conversation

Treat Mythos as a pair programmer. Each round:

1. Ask for a specific component (e.g., 'Write a kernel thread that deallocates the surface concurrently with another thread accessing it').
2. Test the output in a VM or bare metal (use a second M5 Mac for safety).
3. Feed crash logs back to Mythos: 'The kernel panicked at address 0x... with a SMAP violation. How do I disable SMAP for this memory region?'
4. Refine until the crash is a controlled memory corruption.

The team reported that Mythos's ability to understand context and regenerate based on error messages accelerated debugging from weeks to hours.

Step 5: Bypassing Modern Mitigations

Apple Silicon M5 includes:

• Pointer Authentication (PAC) – ensures function pointers are signed.
• Page Protection Layer (PPL) – prevents RWX pages in kernel.
• KASLR – randomizes kernel base.

Mythos suggested using a data-only attack: corrupt a vtable pointer in an IOSurface object’s instance to redirect control flow to a PAC-authorized gadget. The AI provided a list of gadgets from the kernel cache (e.g., sysctl_handle_string) that are already signed. It also generated code to leak the kernel base via a side-channel (timing) and then compute PAC signatures using a known PAC oracle.

Step 6: Achieving Code Execution

Combine all pieces:

1. Trigger the use-after-free to overwrite the vtable pointer.
2. Call a method on the corrupted object—execution jumps to your chosen gadget.
3. Use the gadget to escalate privileges (e.g., call proc_ucred manipulation).
4. Spawn a root shell.

Mythos helped generate the final shellcode that stays within the kernel's PAC constraints. After five days of iterative prompting and testing, the exploit reliably yielded root privileges on M5 macOS 14.5.

Common Mistakes

• Over-relying on AI without understanding the code: Mythos can produce plausible but incorrect kernel code (e.g., missing locks, reference counting errors). Always review each snippet manually.
• Not providing enough context: The AI needs precise information about kernel version, CPU type, and mitigations. Vague prompts lead to generic code that won't work on M5.
• Ignoring crash logs: Kernel panics are your friend. Paste full panic logs to Mythos for better debugging assistance.
• Testing on production machines: Always use a dedicated test device with no important data. Kernel exploits can permanently brick the system.
• Expecting magic: Mythos is a tool, not a replacement for deep kernel expertise. You still need to drive the direction and verify correctness.

Summary

Using Mythos Preview, a team bypassed five years of Apple's kernel security improvements on M5 silicon in just five days. The key was a structured approach: precise prompting, iterative refinement based on crash logs, and leveraging the AI's knowledge of modern mitigations like PAC and KASLR. While AI-assisted exploit development is still nascent, this case shows its potential to dramatically accelerate security research. With careful oversight and genuine technical skill, you can replicate these results for your own targets.