content: Actually, the vulnerability dicussed here requires that you already run code in ring 0. Modern processors also have a ring -1 and -2. Ring -1 is for virtualisation, allowing you to run a hypervisor in ring -1 and run any number of guest operating systems, giving each full access to rings 0-3. Ring -2 is System Management Mode, for BIOS code, advanced power control, hardware debugging, TPM emulation and the like. The design flaw here now allows you to jump from ring 0 to ring -2, bypassing hypervisors and giving you more hardware access. Being in ring -2 also allows you to hide memory you use from the operating system, allowing really sneaky rootkits.