I searched and found this on cpanel forum but not sure what it worked for.I believe the script is located at /usr/local/cpanel/scripts/upcp
run this /usr/local/cpanel/scripts/upcp from ssh?You just need to use /scripts/upcp command and it will get your WHM/Cpanel updated , however before you update the version go through the version updates first which can be found on cpanel site itself.