In LibTIFF 4.0.9, there is a NULL pointer dereference in the TIFFWriteDirectorySec function in tif_dirwrite.c that will lead to a denial of service attack, as demonstrated by tiffset.Referenceshttp://www.securityfocus.com/bid/105932https://usn.ubuntu.com/3906-1/https://lists.debian.org/debian-lts-announce/2019/02/msg00026.htmlhttp://bugzilla.maptools.org/show_bug.cgi?id=2820http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00041.htmlhttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TX5UEYHGMTNEHJB4FHE7HCJ75UQDNKGB/https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/C6IL2QFKE6MGVUTOPU2UUWITTE36KRDF/https://seclists.org/bugtraq/2019/Nov/5http://packetstormsecurity.com/files/155095/Slackware-Security-Advisory-libtiff-Updates.htmlhttps://security.gentoo.org/glsa/202003-25https://www.debian.org/security/2020/dsa-4670
