The ucode_ioctl function in intel/io/ucode_drv.c in Sun Solaris 10 and OpenSolaris snv_69 through snv_133, when running on x86 architectures, allows local users to cause a denial of service (panic) via a request with a 0 size value to the UCODE_GET_VERSION IOCTL, which triggers a NULL pointer dereference in the ucode_get_rev function, related to retrieval of the microcode revision.