Failure to validate the value in APCB may allow a privileged attacker to tamper with the APCB token to force an out-of-bounds memory read potentially resulting in a denial of service.
https://www.amd.com/en/corporate/product-security/bulletin/AMD-SB-5001
https://www.amd.com/en/corporate/product-security/bulletin/AMD-SB-3002