AccessData has released version 188.8.131.52 of Cassandra, for use with the KFF. This release addresses issues with supporting Java 8u161 (see attached release notes).
The installer can be found on the KFF 6.4 ISO for use with the 6.4 line of AccessData products, or can be downloaded from here (password: abc123!) for use with the 6.3 line of products (you will still need version 6.3 of the KFF Import Utility from the KFF 6.3 ISO).
Any version of Cassandra can be used with the 6.3 and newer lines of AccessData products. However, you must use the version of the KFF Import Utility that corresponds with the version of your AccessData software (i.e. you must use version 6.4 of the KFF Import Utility to import the KFF data to use with FTK 6.4).