>Ring -2 is one of the highest privilege levels on a computer, running above Ring -1 (used for hypervisors and CPU virtualization) and Ring 0, which is the privilege level used by an operating system's Kernel.
>The Ring -2 privilege level is associated with modern CPUs' System Management Mode (SMM) feature. SMM handles power management, hardware control, security, and other low-level operations required for system stability.
>Due to its high privilege level, SMM is isolated from the operating system to prevent it from being targeted easily by threat actors and malware.
>Tracked as CVE-2023-31315 and rated of high severity (CVSS score: 7.5), the flaw was discovered by IOActive Enrique Nissim and Krzysztof Okupski, who named privilege elevation attack 'Sinkclose.'
>Full details about the attack will be presented by the researchers at tomorrow in a DefCon talk titled "AMD Sinkclose: Universal Ring-2 Privilege Escalation."
>The researchers report that Sinkclose has passed undetected for almost 20 years, impacting a broad range of AMD chip models.
>Ring -2 is isolated and invisible to the OS and hypervisor, so any malicious modifications made on this level cannot be caught or remediated by security tools running on the OS.
>Okupski told Wired that the only way to detect and remove malware installed using SinkClose would be to physically connect to the CPUs using a tool called a SPI Flash programmer and scan the memory for malware.
Access to Ring 0 on Windows is trivial:
>[...] Advanced Persistent Threat (APT) actors, like the North Korean Lazarus group, have been using BYOVD (Bring Your Own Vulnerable Driver) techniques or even leveraging zero-day Windows flaws to escalate their privileges and gain kernel-level access.
>Ransomware gangs also use BYOVD tactics, employing custom EDR killing tools they sell to other cybercriminals for extra profits.
>The notorious social engineering specialists Scattered Spider have also been spotted leveraging BYOVD to turn off security products.
>These attacks are possible via various tools, from Microsoft-signed drivers, anti-virus drivers, MSI graphics drivers, bugged OEM drivers, and even game anti-cheat tools that enjoy kernel-level access.
Whose lucky Russian \ Chinese state APT group will pounce on this to create another bootkit?
@graf@anonaccount@j I just realized: KVM is Ring-0 and Frantech is all EPYC, and this vulnerability is unpatchable. How does any VPS provider that has AMD gear deal with this?
> The patch requires a bios flash or a microcode update
Reasonable.
> One article I read also implies that the malware has to be loaded during boot
Guess we'll have to wait; it sounds like anyone with Ring-0 can do it if they're talking about infected drivers triggering the vulnerability. You don't need to care about which ring you're in if you can intercept the boot process, so it would be a nothingburger if that's the case.
@phnt@p@anonaccount@graf Even then a VM shouldn't have ring-0. You'd have to find a way to break out of the VM and also escalate privileges. I'm not saying it's impossible.
It's hard to say how big of a threat this is without more info.
It's likely a way bigger issue for Windows users. Not out of the ordinary to run stuff downloaded from websites as administrator on that OS.
@graf@j@p@anonaccount Makes sense, it's probably a concern only for VPS and server providers that effectively allow running any code on their machines. If company systems get infected by this, it was game over long before that.