Oracle ORA-7445 [kkzufst] errors in alertlog.

ORA-7445 [kkzufst] errors in alertlog are result from bugs in materialized views refresh jobs.

If you got these bugs you'll see these kind of errors in your database alertlog
(there is always ORA-07445 and kkzufst in error but other clauses can vary.):
--
Exception [type: SIGSEGV, Address not mapped to object] [ADDR:0x1000] [PC:0x44BBFCE, kkzufst()+111] [flags: 0x0, count: 1]
Errors in file...
ORA-07445 : exception encountered: core dump [kkzufst()+111] ...
Incident details in:...
--

In incident log you'll see something like this (here you can also see problematic SQL or PL/SQL clause in "Current SQL Statement ..." section)
(there is always ORA-07445 and kkzufst in error but other clauses can vary.):
--
Exception [type: SIGSEGV, Address not mapped to object] [ADDR:0x1000] [PC:0x44BBFCE, kkzufst()+111] [flags: 0x0, count: 1]
.
.
.
dbkedDefDump(): Starting a non-incident diagnostic dump (flags=0x3, level=3, mask=0x0)
----- Current SQL Statement for this session (sql_id=...

--


Fixes:
Bugs are more accurately 9554075 and 9656434
These both bugs are fixed in Oracle version 11.2.0.2 SPS (Server Patch Set).
And in Oracle version 12 fixes are in following versions: 9554075 -> version Oracle 12.1.0.1 (Base Release). 9656434 -> version Oracle 12.2 (Future release. (Not yet released))


More info about these bugs can be find from MOS (My Oracle Support) document:  
1288415.1