Hello,
I have been using VC++ and the Win32 And Windows SDK for 20 years, and was head hunted by Microsoft 4 times, to work in various R&D departments, over a 15 year period. :)
With Windows, Security is a massive topic and is layerised. Security is implemented in both horizontal and vertical layers of the Windows user/Application-mode and Kernel-mode parts of WIndows - as a general overview.
Security is provided by VC++ to C++ Developers, for all processes created, memory objects created, file objects created etc, at both application level(user mode), and for those developing anti-virus like applications.. kernel-mode levels.
With shared memory, application or user mode level security should suffice, to prevent other identically priviledged processes from accessing a shared memory object allocated by your parent process. Not sure if this would work for Admin level priviledges carrying processes though(who may wish to peek in to your Shared Mem object space).
Rest assured, Windows 10 takes process-level and Object-level security EXTREMELY seriously and both the Windows Win32 API/SDK and kernel-mode Windows DDK(Device Driver Kit) will support various methods of securing a shared mem object/pool/space.
Just some insights... :)