[exim] core dump in host.c

Ok, it is not a recent version of exim - but it has been
running for several years and does nice work, but it is 4.34

So it suddenly started dumping cores, looking into them they
are all spams from 213.198.89.166 which resolves from
166.89.198.213.in-addr.arpa to PTR ".", makes our exim
abort with core dump.

Does anybody else see this, could it be a possible exploit?
exim luckily runs with the initial uid, not as root, when
the disaster occurs.

hmk