An issue was discovered in NvmExpressDxe 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 variable EFI_BOOT_SERVICES. This allows an attacker who is capable of executing code in DXE phase to exploit this vulnerability to escalate privileges to SMM. The attacker can overwrite the LocateProtocol or Freepool memory address location to execute unwanted code.