libXcursor before 1.1.15 has various integer overflows that could lead to heap buffer overflows when processing malicious cursors, e.g., with programs like GIMP. It is also possible that an attack vector exists against the related code in cursor/xcursor.c in Wayland through 1.14.0.
https://www.debian.org/security/2017/dsa-4059
https://usn.ubuntu.com/3622-1/
https://security.gentoo.org/glsa/201801-04
https://marc.info/?l=freedesktop-xorg-announce&m=151188036018262&w=2
https://lists.freedesktop.org/archives/wayland-devel/2017-November/035979.html
https://lists.debian.org/debian-lts-announce/2017/12/msg00002.html
https://cgit.freedesktop.org/wayland/wayland/commit/?id=5d201df72f3d4f4cb8b8f75f980169b03507da38
https://bugzilla.suse.com/show_bug.cgi?id=1065386
http://www.ubuntu.com/usn/USN-3501-1
http://www.openwall.com/lists/oss-security/2017/11/28/6
http://security.cucumberlinux.com/security/details.php?id=156