The GDM daemon in GNOME Display Manager (GDM) before 2.14.13, 2.16.x before 2.16.7, 2.18.x before 2.18.4, and 2.19.x before 2.19.5 does not properly handle NULL return values from the g_strsplit function, which allows local users to cause a denial of service (persistent daemon crash) via a crafted command to the daemon's socket, related to (1) gdm.c and (2) gdmconfig.c in daemon/, and (3) gdmconfig.c and (4) gdmflexiserver.c in gui/.