Endless recursion in xkbcomp/expr.c resulting in a crash. (CVE-2018-15853) NULL pointer dereference when parsing invalid atoms in ExprResolveLhs resulting in a crash. (CVE-2018-15859) NULL pointer dereference in ExprResolveLhs resulting in a crash. (CVE-2018-15861) NULL pointer dereference in ResolveStateAndPredicate resulting in a crash. (CVE-2018-15863)