Possibility of submitting a paper whose one page has been previously accepted in a poster session?
Only the conference committee can really answer that, but I offer two suggestions. These apply even if the conference committee sees no problem. 

There is a concept called self-plagiarism, that I think is a bit stupid, but it exists and many consider it a serious issue. You should, at a minimum cite your own earlier work (the poster) just as you would cite anyone else and quote it appropriately. 

The second suggestion is that, while you still cite the poster work, you re-write it, incorporating the important ideas rather than quoting it directly. 

But you will run in to trouble with some if you just use it without comment even though it is your own work. 

I doubt that the field matters much. My field is also CS, however.