Systems, methods, and apparatuses for defending against cross-privilege linear access are described. For example, an implementation of an apparatus comprising privilege level storage to store a current privilege level and address check circuitry coupled to the privilege level storage, wherein the address check circuitry is to determine whether a linear address associated with an instruction is allowed to access a partition of a linear address space of the apparatus based upon a comparison of the current privilege level and a most significant bit of the linear address is described.