An issue was discovered in CPUID cpuz.sys 1.0.5.4. An attacker can use DeviceIoControl with the unvalidated parameters 0x9C402440 and 0x9C402444 as IoControlCodes to perform RDMSR and WRMSR, respectively. Through this process, the attacker can modify MSR_LSTAR and hook KiSystemCall64. Afterward, using Return-Oriented Programming (ROP), the attacker can manipulate the stack with pre-prepared gadgets, disable the SMAP flag in the CR4 register, and execute a user-mode syscall handler in the kernel context. It has not been confirmed whether this works on 32-bit Windows, but it functions on 64-bit Windows if the core isolation feature is either absent or disabled.