The XListFonts function in X.org libX11 before 1.6.4 might allow remote X servers to gain privileges via vectors involving length fields, which trigger out-of-bounds write operations.
www.openwall.com/lists/oss-security/2016/10/04/2
www.openwall.com/lists/oss-security/2016/10/04/4
www.securityfocus.com/bid/93362
www.securitytracker.com/id/1036945
cgit.freedesktop.org/xorg/lib/libX11/commit/?id=8c29f1607a31dac0911e45a0dd3d74173822b3c9
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GMCVDXMFPXR7QGMKDG22WPPJCXH2X3L7/
lists.x.org/archives/xorg-announce/2016-October/002720.html
security.gentoo.org/glsa/201704-03
usn.ubuntu.com/3758-1/
usn.ubuntu.com/3758-2/