diff --git a/lib/dns/resolver.c b/lib/dns/resolver.c
index f153e54d4d3..5997f8deec2 100644
--- a/lib/dns/resolver.c
+++ b/lib/dns/resolver.c
@@ -212,6 +212,17 @@
  */
 #define NS_FAIL_LIMIT 4
 #define NS_RR_LIMIT   5
+/*
+ * IP address lookups are performed for at most NS_PROCESSING_LIMIT NS RRs in
+ * any NS RRset encountered, to avoid excessive resource use while processing
+ * large delegations.
+ */
+#define NS_PROCESSING_LIMIT 20
+
+STATIC_ASSERT(NS_PROCESSING_LIMIT > NS_RR_LIMIT,
+	      "The maximum number of NS RRs processed for each delegation "
+	      "(NS_PROCESSING_LIMIT) must be larger than the large delegation "
+	      "threshold (NS_RR_LIMIT).");
 
 /* Hash table for zone counters */
 #ifndef RES_DOMAIN_HASH_BITS
@@ -3543,6 +3554,7 @@ fctx_getaddresses(fetchctx_t *fctx, bool badcache) {
 	bool need_alternate = false;
 	bool all_spilled = true;
 	unsigned int no_addresses = 0;
+	unsigned int ns_processed = 0;
 
 	FCTXTRACE5("getaddresses", "fctx->depth=", fctx->depth);
 
@@ -3733,6 +3745,11 @@ fctx_getaddresses(fetchctx_t *fctx, bool badcache) {
 
 		dns_rdata_reset(&rdata);
 		dns_rdata_freestruct(&ns);
+
+		if (++ns_processed >= NS_PROCESSING_LIMIT) {
+			result = ISC_R_NOMORE;
+			break;
+		}
 	}
 	if (result != ISC_R_NOMORE) {
 		return (result);