An issue was discovered in Insyde InsydeH2O with kernel 5.2 through 5.5. The Save State register is not checked before use. The IhisiSmm driver does not check the value of a save state register before use. Due to insufficient input validation, an attacker can corrupt SMRAM.
https://www.insyde.com/security-pledge/SA-2023022
https://www.insyde.com/security-pledge
https://research.nccgroup.com/2023/04/11/stepping-insyde-system-management-mode/