In LibTIFF 4.0.9, there is a Null-Pointer Dereference in the tif_print.c TIFFPrintDirectory function, as demonstrated by a tiffinfo crash.
https://www.debian.org/security/2018/dsa-4100
https://usn.ubuntu.com/3606-1/
https://usn.ubuntu.com/3602-1/
https://lists.debian.org/debian-lts-announce/2018/01/msg00034.html
https://lists.debian.org/debian-lts-announce/2018/01/msg00033.html
https://gitlab.com/libtiff/libtiff/commit/c6f41df7b581402dfba3c19a1e3df4454c551a01