Linux cryptographic code flaw offers fast route to root

A newly disclosed local privilege escalation vulnerability in the Linux kernel's authencesn cryptographic template (CVE-2026-31431, "Copy Fail") allows an unprivileged user to write four controlled bytes into the page cache of any readable file, enabling modification of setuid binaries to gain root; a small Python proof-of-concept exists and major Linux distributions have issued patches. The flaw is not remotely exploitable by itself but can be chained with RCE or compromised CI/SSH sessions and poses particular risk to multi-tenant systems, containers, and Kubernetes nodes.