In the kernel in Insyde InsydeH2O 5.x, certain SMM drivers did not correctly validate the CommBuffer and CommBufferSize parameters, allowing callers to corrupt either the firmware or the OS memory. The fixed versions for this issue in the AhciBusDxe, IdeBusDxe, NvmExpressDxe, SdHostDriverDxe, and SdMmcDeviceDxe drivers are 05.16.25, 05.26.25, 05.35.25, 05.43.25, and 05.51.25 (for Kernel 5.1 through 5.5).

An issue was discovered in IdeBusDxe in Insyde InsydeH2O 5.x. Code in system management mode calls a function outside of SMRAM in response to a crafted software SMI, aka Inclusion of Functionality from an Untrusted Control Sphere. Modifying the well-known address of this function allows an attacker to gain control of the system with the privileges of system management mode.