First Apple M5 memory exploit discovered using Anthropic AI, gives root access on MacOS — Claude Mythos helps security researchers bypass Memory Integrity Enforcement

Thanks to AI-assisted security research, hackers with hats of various colors are finding exploits everywhere. Linux has had its worst week in years with the CopyFail and Dirty Frag root-gaining vulnerabilities, and things aren't much rosier at Microsoft, thanks to the YellowKey BitLocker bypass, as well as GreenPlasma and RedSun privilege-gaining exploits. Now, it's Apple's turn with a local privilege escalation that gets past the M5 chips' much-vaunted Memory Integrity Enforcement (MIE).

There aren't many technical details, but the vulnerability is simple in practice: run a command as a standard user and gain root (administrator) access to the machine. Macs are rarely servers, so the practical impact is limited. However, the exploit remains concerning, as it's relatively easy to trick a user into running it and, with full system control, also hard to find and remove. The research team in question is named Calif, and as far as they know, the boffins there are the only ones making a public disclosure of this issue. Such assumptions are tricky in this day and age, though.

Mercifully for Captain Cook's ship, instead of being a zero-day reveal out of nowhere that left systems administrators scrambling, the exploit in question was disclosed to the company in advance (in person, no less). Calif published the vulnerability overview as part of a series of blog posts called the Month of AI-Discovered Bugs, since this new Apple vulnerability falls within a set of security findings aided by AI tools — in this case, Anthropic's Mythos Preview.

The researchers tested their code on an Apple M5 machine and macOS 26.4.1. The exploit chain impressively sneaks past MIE, a security feature present on M5 and A19 chips that labels each 16-byte memory slice with a 4-bit tag associated with the pointers that use it. MIE is enforced at the hardware level in a hypervisor-like configuration and effectively protects against most common classes of security exploits, namely, but not only, buffer overflows and use-after-free vulnerabilities.

As an oversimplification, MIE ensures that any memory read or write operation acts on the data that it was originally meant to, even at the kernel level. If that doesn't happen, either your application has a bug, or someone's up to shenanigans. The base feature is part of ARM MTE, and MIE is an Apple-added layer that enforces the said checks at the hardware level, with purportedly little to no performance overhead, and only 3% memory wastage. This blog post goes into more detail on the subject, and it's quite an interesting read.

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