A NULL pointer dereference in the function _TIFFmemcmp at tif_unix.c (called from TIFFWriteDirectoryTagTransferfunction) in LibTIFF 4.0.9 allows an attacker to cause a denial-of-service through a crafted tiff file. This vulnerability can be triggered by the executable tiffcp.
https://www.debian.org/security/2020/dsa-4670
https://usn.ubuntu.com/3906-1/
https://lists.debian.org/debian-lts-announce/2019/02/msg00026.html
http://www.securityfocus.com/bid/105342
http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00041.html