Khanh:

Early this week, we had a meeting at Apple Park in Cupertino. While there, we also shared with Apple our latest vulnerability research report: the first public macOS kernel memory corruption exploit on M5 silicon, surviving MIE. It was laser printed, in honor of our hacker friends.

[…]

The exploit is a data-only kernel local privilege escalation chain targeting macOS 26.4.1 (25E253). It starts from an unprivileged local user, uses only normal system calls, and ends with a root shell. The implementation path involves two vulnerabilities and several techniques, targeting bare-metal M5 hardware with kernel MIE enabled.

[…]

We didn’t build the chain alone. Mythos Preview helped identify the bugs and assisted throughout exploit development.

Previously:

• Hardening Firefox With Mythos
• curl Removes Bug Bounties
• Mythos and Glasswing
• Memory Integrity Enforcement

Update (2026-05-26): ironPeak (via Patrick Wardle):

MIE is a real improvement. EMTE stops most pointer corruption, the RO zone keeps the crown jewels behind a hardware gate, and the Secure Page Table Monitor enforces that only one function can open it. All of that did its job. And it didn’t catch this one.

The bug was in the one place MIE can’t protect: the argument validation of the trusted writer itself. An integer overflow in _zalloc_ro_mut’s stack-area filter let attacker bytes spill across slot boundaries inside the RO zone. The bytes landed on a ucred. The cr_uid flipped to zero. Root shell. The pointer was never bad, the page table was never wrong, the tag was always correct.

See also: Hacker News.

Apple M5 Artificial Intelligence Bug Claude Exploit Kernel Mac macOS Tahoe 26 Mythos Programming Security

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