You can take the GRE for CS without being a student, as proof of your knowledge. I have heard of very rare cases where people have been admitted to a professional master's program (different from the regular master's program in that it's meant for working professionals) without having a degree.

The Computer Science GRE was discontinued a few years ago.

Good question. Are there any accredited graduate programs or professional programs that will accept students without undergrad degrees but with good GRE scores?

No undergrad at all? That would be fairly rare.

Non CS undergrad? Lots of universities have programs or tracks for CS masters from a non-CS background.

I have seen a few universities set up accelerated professional CS BA/BS in the past five years or so.

A more common path that I have seen from self thought developers that "needed the degree" has been doing a reputable local or online BA/BS part-time.

edit: grammar & formating