PAGEEXECUTEREAD

PAGE_EXECUTE_READ is a memory protection constant used in the Windows API to specify the access rights of a region of virtual memory. It indicates that the pages can be both executed and read, but cannot be written. The constant is part of the PAGE_ family of protection flags defined in the Windows headers.

In practice, PAGE_EXECUTE_READ is supplied to memory management functions such as VirtualAlloc and VirtualProtect to set the protection attributes of a memory region. The Windows API requires one of the PAGE_ constants for the protection parameter; PAGE_EXECUTE_READ is not typically combined with other access flags. A region marked with PAGE_EXECUTE_READ allows running code stored in that region and reading its contents, but attempts to write to the region will raise a protection fault.

Common usage patterns include dynamic code generation and Just-In-Time compilation, where generated code needs to be executable and readable but not writable once finalized. If a program must modify the code region, it must first change the protection to a writable variant (for example PAGE_EXECUTE_READWRITE or PAGE_READWRITE), perform the modification, and then restore PAGE_EXECUTE_READ to maintain security guarantees.

Security considerations emphasize the principle of W^X (write XOR execute): keeping memory regions non-writable after code is generated reduces the risk of exploits. PAGE_EXECUTE_READ is often used in conjunction with security features such as the NX bit to prevent unintended code modification.

See also PAGE_EXECUTE, PAGE_EXECUTE_READWRITE, VirtualAlloc, and VirtualProtect for related memory protection concepts.