AMD is warning about a high-severity CPU vulnerability named SinkClose that impacts multiple generations of its EPYC, Ryzen, and Threadripper processors. The vulnerability allows attackers with Kernel-level (Ring 0) privileges to gain Ring -2 privileges and install malware that becomes nearly undetectable.
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.”
But if you can get around the signing requirements, it would be trivial to make the psp firmware only do that. (Probably not trivial, but at least technically feasable)
I did want to expand on this, I’d be curious as to what Jeremy Soller found getting certain Ryzen mobile platforms working with coreboot.
Perhaps we’ll need to wait for OpenSIL for more comprehensive support.
Aside from x86 core init, PSP is still required for specific OS security requirements. Can at least take solace in the fact that OEMs seem to have completely turned down MS Pluton.