Is it required for students applying to PhD programs in CS to have a very specific problem in mind before they can apply/be accepted to graduate school? Or do p

Is it required for students applying to PhD programs in CS to have a very specific problem in mind before they can apply/be accepted to graduate school? Or do professors work with you to find a problem? Heard I absolutely cannot get into graduate school unless I have a very specific use case of a research problem I want to solve. Thought this would be difficult given my lack of knowledge in problems 'worth solving' before graduate studies. I do have a field of interest I want to go into and a broad problem I was to solve, but heard I need a very, very specific problem to propose before I can apply to graduate school.