Anthropic says its AI wrote a working attack that lets a stranger take full control of a Linux server over the internet, no password needed. The bug behind it, CVE-2026-98432, has been hiding in Linux since version 4.4 and scores 9.8 out of 10 for severity. Linux runs countless servers, and Ubuntu is one of its most popular flavors. Ubuntu's own tracker still lists every version from 16.04 to 26.10 as vulnerable.