I also have a nearly complete implementation of this in Haskell. https://github.com/orclev/CBOR

The main problem it currently faces is that the encoding/decoding support for half-width floats is currently wrong, but so long as you avoid half-width floats it works perfectly.

Eventually I want to add support for encoding indefinite lists by way of one of the streaming libraries like conduit or pipes, but before I do that I need to refactor to the code to break the Binary instances out from the types.