The handles window in process Explorer has a column Access which supposedly determines the access rights of that particular handle. I am not able to get any documentation on how to read the flags and what each bit means. Any resource to point me in the direction would be very helpful.
I believe you can find those defined in winnt.h. (A sample winnt.h which seems to match correctly can be found included in the Wine project.) The lower 16 bits are context-dependent (eg. they are interpreted differently depending on whether the handle is for a file, a threat, a process, etc.)
The bit patterns can be further described in MSDN.