Which CMIS API / version are you using? With CMIS 1.1 Browser binding you should only get the UUID with the version suffix, not the whole NodeRef + version.
Anyway, it should be quite simple to just split the object ID on the client side to only extract the UUID, i.e. take antyhing between last '/' and first ';', between start and first ',' (if no '/' found), or entire object ID (if no '/' and no ';' found, i.e. in CMIS 1.1 object ID for a folder).