There's probably thousands if not more. The way I always imagined this working was. agency and company work together to leave gaps in our hardware and software under the ruse of "it must be secure enough for our use." Agencies get a preemptive six months or so to find enough zero days to do what they want. The engineers at the company screaming about the issues are ignored.

Eventually a foreign adversary or domestic hacker finds one that can cause a lot of harm. As soon as they find one a DOD funded student simultaneously discovers it. Alternatively, if documents leak showing how these exploits could happen, same scenario.

Not to say all bugs are known, but I'd imagine a fair deal of them certainly are.