The IS-IS parser in tcpdump before 4.9.2 has a buffer over-read in print-isoclns.c:isis_print_extd_ip_reach().
https://support.apple.com/HT208221
https://security.gentoo.org/glsa/201709-23
https://github.com/the-tcpdump-group/tcpdump/commit/979dcefd7b259e9e233f77fe1c5312793bfd948f
https://access.redhat.com/errata/RHEA-2018:0705
http://www.tcpdump.org/tcpdump-changes.txt