Hw64.sys in Marvin Test HW.exe before 5.0.5.0 allows unprivileged user-mode processes to arbitrarily map physical memory with read/write access via the MmMapIoSpace API (IOCTL 0x9c40a4f8, 0x9c40a4e8, 0x9c40a4c0, 0x9c40a4c4, 0x9c40a4ec, and seven others), leading to a denial of service (BSOD).