An issue was discovered in AhciBusDxe in the kernel 5.0 through 5.5 in Insyde InsydeH2O. There is an SMM callout that allows an attacker to access the System Management Mode and execute arbitrary code. This occurs because of Inclusion of Functionality from an Untrusted Control Sphere.

A vulnerability exists in SMM (System Management Mode) branch that registers a SWSMI handler that does not sufficiently check or validate the allocated table variables EFI_BOOT_SERVICES and EFI_RUNTIME_SERVICES. This can be used by an attacker to overwrite address location of the function (LocateHandleBuffer) to the address location of arbitrary code controlled by the attacker. On system call to SWSMI handler, the arbitrary code can be triggered to execute.