Hello,

At present, SEP SBE 12.1 RU1 MP1 is the Latest.

Check this Article:

What are the Symantec Endpoint Protection (SEP) versions released officially?

Incase if you are looking forward to migrate from Symantec Endpoint Protection SBE 12.1.671.4971 to Symantec Endpoint Protection SBE 12.1 RU1 MP1, then you may have to follow this Migration path as provided below:

SEP SBE 12.1.671 >> SEP SBE 12.1 RU1 >> SEP SBE 12.1 RU1 MP1

However, within coming days we would see the release of SEP SBE 12.1 RU2 in which you may be able to migrate from -

SEP SBE 12.1.671 >> SEP SBE 12.1 RU2

(I believe it would be worth a wait...)

Check these Articles:

Knowledgebase Articles for Symantec Endpoint Protection SBE 12.1. RU2

https://www-secure.symantec.com/connect/articles/knowledgebase-articles-symantec-endpoint-protection-sbe-121-ru2

Supported upgrade paths for Symantec Endpoint Protection Manager

http://www.symantec.com/docs/HOWTO81442

Supported upgrade paths for the Symantec Endpoint Protection Small Business Edition client

http://www.symantec.com/docs/HOWTO81443

Hope that helps!!!