TLS 1.2 is supported on 12.9 SP1 and later along with JDK 1.8.
JDK 1.8 can be used on 12.8 CF3 also but TLS 1.2 is not certified and not supported on 12.8.
It is needed to upgrade to 12.9 SP2 (as 12.9 SP1 is obsolete) and later versions to support TLS1.2.