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://marc.info/?l=freedesktop-xorg-announce&m=151188036018262&w=2
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
https://usn.ubuntu.com/3622-1/
https://security.gentoo.org/glsa/201801-04
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