Hi,
Thank you for posting in Symantec community.
I would be glad to answer your query.
SEP 12.1 RU4MP1b (12.1.4112.4156) is the latest version. It seems you have SEP 12.1 RU4 ( 12.1.4100.4126)
You need to upgrade the SEPM to the latest version & it will add SEP 12.1 RU4MP1b packages in the console. Upgrade of SEPM is necessary to cover open SSL vulnerability. In case you haven't seen this info here are more details: http://www.symantec.com/docs/TECH216558
OR
You will have to manually import the packages into the console (Not recommended for you)
After successful SEPM upgrade, upgrade the clients either using Auto upgrade OR Client deployment wizard (CDW)
Article for reference: https://www-secure.symantec.com/connect/articles/sepm-121-auto-upgrad