The TIFFWriteDirectorySec() function in tif_dirwrite.c in LibTIFF through 4.0.9 allows remote attackers to cause a denial of service (assertion failure and application crash) via a crafted file, a different vulnerability than CVE-2017-13726.
https://www.debian.org/security/2018/dsa-4349
https://usn.ubuntu.com/3864-1/
https://lists.debian.org/debian-lts-announce/2018/07/msg00002.html