If you want to update your version of Cordova to the latest version, or you want to revert to an earlier version (to test or debug), here are the steps to follow. I also have instructions on updating the plugins and platform versions here.
Resource:
https://github.com/apache/cordova-docs/blob/master/docs/en/5.0.0/guide/cli/index.md
Cordova blog for latest updates:
http://cordova.apache.org/blog/