Btw, keep in mind that DLL/PE shared sections and shared memory (CreateFileMapping etc) are two different IPC mechanisms.
Research notesTL;DR: It's hard (though possible) to find apps that use DLL shared sections; it's even harder to find an interesting and used variable in such section. So I guess the bug class is not dead yet, but it's nothing exciting or commonly encountered. The Cygwin bug was in a shared section in cygwin1.dll - there was a UNICODE_STRING object there that was copied (unbounded copy) to a buffer on the stack on application start, with no stack cookies in sight.
DLL shared sections: a ghost of the past (PDF EN; Update 1)
ToolsI've created and released two small tools:
* FindShared can be used to locate all PE files with a shared+writable section on the disk
* StressShared is a naive fuzzer for shared sections
Project page on code.google.com (link)
DLLSharedSections-2012.05.19.zip (Win32 EXE + SRC)
Cygwin exploitation demoDetails about the bug as well as the timeline are in the second part of the research notes.