Copy.Fail Linux Vulnerability

This is the worst Linux vulnerability in years.

TL;DR

• copy.fail is a Linux kernel local privilege escalation, not a browser or clipboard attack. Disclosed by Theori on 29 April 2026 with a working PoC.
• It abuses the kernel crypto API (AF_ALG sockets) plus splice() to write four bytes at a time straight into the page cache of a file the attacker does not own.
• The exploit works unmodified across Ubuntu, RHEL, Debian, SUSE, Amazon Linux, Fedora and most others. No race condition, no per-distro offsets.
• The file on disk is never modified. AIDE, Tripwire and checksum-based monitoring see nothing.
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