diff -Naur -x '*.orig' -x '*.rej' ldns-1.6.17/str2host.c ldns-1.6.17-check-parse-limit/str2host.c
--- ldns-1.6.17/str2host.c	2014-01-10 22:04:41.000000000 +0100
+++ ldns-1.6.17-check-parse-limit/str2host.c	2017-12-28 19:03:16.351196408 +0100
@@ -1458,8 +1458,10 @@
 	if (! str) {
 		return LDNS_STATUS_SYNTAX_BAD_ESCAPE;
 	}
-	length = (size_t)(dp - data);
-
+	if (!(length = (size_t)(dp - data))) {
+		LDNS_FREE(data);
+		return LDNS_STATUS_SYNTAX_EMPTY;
+	}
 	/* Lose the overmeasure */
 	data = LDNS_XREALLOC(dp = data, uint8_t, length);
 	if (! data) {