Improper input validation for DIMM serial presence detect (SPD) metadata could allow an attacker with physical access, ring0 access on a system with a non-compliant DIMM, or control over the Root of Trust for BIOS update, to bypass SMM isolation potentially resulting in arbitrary code execution at the SMM level.
https://www.amd.com/en/resources/product-security/bulletin/AMD-SB-5007.html
https://www.amd.com/en/resources/product-security/bulletin/AMD-SB-4012.html
https://www.amd.com/en/resources/product-security/bulletin/AMD-SB-3014.html