DMA attacks on the parameter buffer used by a software SMI handler used by the driver PcdSmmDxe could lead to a TOCTOU attack on the SMI handler and lead to corruption of other ACPI fields and adjacent memory fields. DMA attacks on the parameter buffer used by a software SMI handler used by the driver PcdSmmDxe could lead to a TOCTOU attack on the SMI handler and lead to corruption of other ACPI fields and adjacent memory fields. The attack would require detailed knowledge of the PCD database contents on the current platform. This issue was discovered by Insyde engineering during a security review. This issue is fixed in Kernel 5.3: 05.36.23, Kernel 5.4: 05.44.23, Kernel 5.5: 05.52.23. Kernel 5.2 is unaffected. CWE-787 An issue was discovered in Insyde InsydeH2O with kernel 5.0 through 5.5. DMA attacks on the parameter buffer that is used by a software SMI handler (used by the PcdSmmDxe driver) could lead to a TOCTOU race-condition attack on the SMI handler, and lead to corruption of other ACPI fields and adjacent memory fields. The attack would require detailed knowledge of the PCD database contents on the current platform.