For people unable to upgrade due to a problem with curl. Running Code: apt-get install curl will fix the dependency by installing the latest version of curl and libcurl3 and will allow you to do the CSSU update.
apt-get install curl
$ curl -sh: curl: not found # apt-get install curl Reading package lists... Done Building dependency tree Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: curl: Depends: libcurl3 (= 7.26.0-1maemo1+0cssu1) but 7.26.0-1maemo1+0cssu3 is to be installed E: Broken packages