When a binary is running and there is some memory/info leak are there areas of program (or OS?) memory which are more prone to leak and is a leak in one segment worse than in another segment?
Generally, programs running in userspace don't have access to kernel space memory. As a result, it is overwhelmingly unlikely that a program would be able to leak kernel memory.
The memory being leaked depends heavily on the program running. A famous example is Heartbleed, which leaked all sorts of information regarding the TLS process and contents of communications of other users. Concretely, this means:
- Private Keys
- Sensitive Personal Data
This, of course, would be the worst case. Some internal states of your program, such as "how many more bytes need to be sent to this user", are of very little relevance to an attacker. Depending on the specific memory leak, it may be possible for an attacker to determine what sort of data is being leaked, or it might be completely random. In the latter case, an attacker would need some form of analysis to determine what the data being leaked means.
For example, if I gave you
01bf7621 6dd8317f 820c5ab1, then you really wouldn't know what that means unless you had some sort of context.