I set the language to "default" (auto-detect - should result in reasonable highlighting for C-like code) for cuda. That shouldn't interfere with anything important (you'll get highlighting now for things like stack traces if you use a code block for them, but that's pretty common anyway - prefix them with
<!-- language: lang-none --> if you care).
FWIW, there's no highlighting available for FORTRAN. So the results of cuda+fortran code blocks are a little... interesting. Again, it can be turned off on a per-block basis if necessary.