Input validation

An issue was discovered on certain Fujitsu LIEFBOOK devices (A3510, U9310, U7511/U7411/U7311, U9311, E5510/E5410, U7510/U7410/U7310, E459/E449) with BIOS versions before v1.09 (A3510), v2.17 (U9310), v2.30 (U7511/U7411/U7311), v2.33 (U9311), v2.23 (E5510), v2.19 (U7510/U7410), v2.13 (U7310), and v1.09 (E459/E449). The FjGabiFlashCoreAbstractionSmm driver registers a Software System Management Interrupt (SWSMI) handler that is not sufficiently validated to ensure that the CommBuffer (or any other communication buffer’s nested contents) are not pointing to SMRAM contents. A potential attacker can therefore write fixed data to SMRAM, which could lead to data corruption inside this memory (e.g., change the SMI handler’s code or modify SMRAM map structures to break input pointer validation for other SMI handlers). Thus, the attacker could elevate privileges from ring 0 to ring -2 and execute arbitrary code in SMM.