We Thought Linux Was a “Hardened” Operating System: a Vulnerability Has Just Shaken Nearly All Its Versions

Theori disclosed CopyFail, a Linux kernel logic flaw tracked as CVE-2026-31431, and published an exploit demonstrating local privilege escalation.

The bug can let a low-privilege local user gain root access, affecting the core of millions of Linux systems.

Although fixes were already present in several kernel branches, many distributions were still rolling out patches or mitigations when the exploit became public.

Debian, Arch, Fedora, SUSE, Amazon Linux, and Ubuntu were among the distributions working to close the exposure window.