Ghosts in the Machine Check: Conjuring Hardware Failures for Privilege Escalation

We’ve all seen it. The sudden freeze. The blue screen of death. The catastrophic system halt.

Usually, when a processor encounters a truly unrecoverable hardware error—a bit flip in the L2 cache, a voltage sag, or a literal "CPU on fire" scenario—it triggers whats called a Machine Check Exception (MCE). The hardware realizes the world no longer makes sense, throws its hands up, and shuts everything down before data corruption can spread. It’s the ultimate fail-safe.

But as security researchers, we have to ask the dangerous question: What happens if we don’t let it shut down?

At DEF CON 33 and Blackhat 2025, I introduced a new class of attack that moves hardware exploitation out of the realm of "accidental cosmic rays" and into the realm of "software-defined chaos." We’re not just waiting for a ghost in the machine; we’re conjuring one.

The Premise: Weaponizing the Panic Button

The Machine Check architecture was designed for reliability, not security. When an MCE occurs, the processor transitions into a highly privileged state to handle the error.

In a "normal" failure, the BIOS or Kernel sees a fatal error and halts. But by using software-only techniques to surgically inject these "fatal" signals at the exact nanosecond a privileged CPU operation is occurring (like a Ring 3 to Ring 0 transition), we can disrupt the CPU’s internal state machine.

We are essentially "glitching" the processor using its own error-reporting logic.

Keeping the Corpse Alive

The core of this research is circumventing the traditional fail-safes. Usually, an MCE is a death sentence for the OS. However, by carefully manipulating the Machine Check banks and timing our "failures," we can force the system to limp along—damaged, but alive.

I call this "Zombie Execution." The processor is in a state it was never meant to be in:

1. It has encountered a "fatal" error.

2. The internal logic has been disrupted.

3. But execution continues.

When you disrupt a secure transition (like a SYSCALL or a VM exit) with a perfectly timed machine check, the processor can lose track of its privilege boundaries. By riding this wave of cascading system failures, we can effectively "teleport" execution into privileged space.

From Chaos to Control

The most "impractical" part of this—which, as you know, is my favorite part—is the recovery.

It’s one thing to crash a kernel by screaming "HARDWARE FAILURE" at it. It’s another thing entirely to:

• Trigger the failure.

• Capture the instruction pointer in a privileged context.

• Undo the damage.

• Patch the "unrecoverable" state in real-time.

• Let the system continue as if nothing happened.

In the demo, we showed how to use these synthesized hardware failures to achieve a cross-ring privilege escalation, gaining hardware-level control without needing a traditional software bug. We aren't exploiting a flaw in the code; we’re exploiting a flaw in the universe’s commitment to reliability.

Why This Matters

This isn't just about a new way to get root. It’s about a new way to look at hardware. As we push processors to be faster and more complex, the gap between "hardware logic" and "architectural intent" grows.

The Machine Check architecture is a massive, complex, and largely untrusted surface area that sits underneath every security boundary we rely on. If we can't trust the processor to fail correctly, we can't trust it to succeed securely.

The ghosts are already in the machine. We’re just finally learning how to talk to them.

Want to dive deeper?

This blog is the tip of the iceburg, there were a lot of really complex challenges to solve in this research, one of my favorite was a very complicated timing challenge that required some innovative thinking, sound interesting? check out the recordings

Defcon 33 [video][slides]

Blackhat 2025 [slides]

Wheres the repo?

Sorry! Its in the works I promise, life has thrown a lot of (interesting) distractions my way.