An issue was discovered in Insyde InsydeH2O with kernel 5.0 through 5.5. DMA attacks on the FvbServicesRuntimeDxe shared buffer used by SMM and non-SMM code could cause TOCTOU race-condition issues that could lead to corruption of SMRAM and escalation of privileges. This attack can be mitigated using IOMMU protection for the ACPI runtime memory used for the command buffer. This attack can be mitigated by copying the firmware block services data to SMRAM before checking it.