Not infinite, obviously, but yes -- complex software will effectively always have additional vulnerabilities. It's a bit like how it's impossible to have a nontrivial logic system that is both complete and correct.

It's a core truth about security that perfect security is impossible to achieve. If there's a legal way to access something, there's also an illegal way. The only question is how much time and effort it requires.

This isn't just a computer thing, by the way. It's just as true for physical security as well.