PAGEEXECUTEREADWRITE

PAGE_EXECUTE_READWRITE is a memory protection constant in the Windows API that designates a memory region which can be read, written, and executed. It is used with functions such as VirtualAlloc and VirtualProtect to set page protection attributes. When a region is marked PAGE_EXECUTE_READWRITE, code stored in those pages can be modified at runtime and subsequently executed by the processor.

Typical use cases include dynamic code generation, just-in-time compilers, loaders that emit executable code, and certain hot-patching scenarios where code must be modified in memory. It is generally used only when the application must rewrite or generate code in memory; otherwise, safer protections are preferred.

Security implications: PAGE_EXECUTE_READWRITE is considered high-risk because it merges writable and executable permissions, enabling potential code injection or memory corruption exploits if an attacker can influence the contents of the region. Modern Windows security practices discourage its use; developers are advised to minimize its lifetime and scope, use PAGE_READWRITE or PAGE_EXECUTE_READ where appropriate, and switch protections to executable-only after code has been written (for example by calling VirtualProtect). Alternatives include allocating separate non-writable executable memory or using JIT techniques that emit to non-executable buffers and then mark them executable when done.

Notes: The constant is defined by the Windows API (in headers such as WinBase.h) and its value is system-dependent (commonly 0x40). It is part of the broader set of memory protection constants used to control paging behavior on Windows, alongside PAGE_READONLY, PAGE_READWRITE, PAGE_EXECUTE, and PAGE_EXECUTE_READ. See also VirtualAlloc, VirtualProtect, DEP, and W^X guidelines.