diff -urp bind-9.3.3/lib/dns/include/dns/validator.h bind-9.3.4/lib/dns/include/dns/validator.h
--- bind-9.3.3/lib/dns/include/dns/validator.h	2006-01-06 01:01:42.000000000 +0100
+++ bind-9.3.4/lib/dns/include/dns/validator.h	2007-01-11 05:51:39.000000000 +0100
@@ -144,6 +144,7 @@ struct dns_validator {
  * dns_validator_create() options.
  */
 #define DNS_VALIDATOR_DLV 1U
+#define DNS_VALIDATOR_DEFER 2U
 
 ISC_LANG_BEGINDECLS
 
@@ -192,6 +193,15 @@ dns_validator_create(dns_view_t *view, d
  */
 
 void
+dns_validator_send(dns_validator_t *validator);
+/*%<
+ * Send a deferred validation request
+ *
+ * Requires:
+ *	'validator' to points to a valid DNSSEC validator.
+ */
+
+void
 dns_validator_cancel(dns_validator_t *validator);
 /*%<
  * Cancel a DNSSEC validation in progress.
diff -urp bind-9.3.3/lib/dns/resolver.c bind-9.3.4/lib/dns/resolver.c
--- bind-9.3.3/lib/dns/resolver.c	2006-08-31 05:57:11.000000000 +0200
+++ bind-9.3.4/lib/dns/resolver.c	2007-01-11 06:05:10.000000000 +0100
@@ -351,6 +356,7 @@ static isc_result_t ncache_adderesult(dn
 				      dns_rdataset_t *ardataset,
 				      isc_result_t *eresultp);
 static void validated(isc_task_t *task, isc_event_t *event); 
+static void maybe_destroy(fetchctx_t *fctx);
 
 static isc_result_t
 valcreate(fetchctx_t *fctx, dns_adbaddrinfo_t *addrinfo, dns_name_t *name,
@@ -369,6 +375,9 @@ valcreate(fetchctx_t *fctx, dns_adbaddri
 	valarg->fctx = fctx;
 	valarg->addrinfo = addrinfo;
 
+	if (!ISC_LIST_EMPTY(fctx->validators))
+		INSIST((valoptions & DNS_VALIDATOR_DEFER) != 0);
+
 	result = dns_validator_create(fctx->res->view, name, type, rdataset,
 				      sigrdataset, fctx->rmessage,
 				      valoptions, task, validated, valarg,
@@ -973,6 +985,8 @@ fctx_query(fetchctx_t *fctx, dns_adbaddr
 	if (result != ISC_R_SUCCESS)
 		return (result);
 
+	INSIST(ISC_LIST_EMPTY(fctx->validators));
+
 	dns_message_reset(fctx->rmessage, DNS_MESSAGE_INTENTPARSE);
 
 	query = isc_mem_get(res->mctx, sizeof(*query));
@@ -3093,12 +3110,21 @@ maybe_destroy(fetchctx_t *fctx) {
 	unsigned int bucketnum;
 	isc_boolean_t bucket_empty = ISC_FALSE;
 	dns_resolver_t *res = fctx->res;
+	dns_validator_t *validator;
 
 	REQUIRE(SHUTTINGDOWN(fctx));
 
-	if (fctx->pending != 0 || !ISC_LIST_EMPTY(fctx->validators))
+	if (fctx->pending != 0 || fctx->nqueries != 0)
 		return;
 
+	for (validator = ISC_LIST_HEAD(fctx->validators);
+	     validator != NULL;
+	     validator = ISC_LIST_HEAD(fctx->validators)) {
+		ISC_LIST_UNLINK(fctx->validators, validator, link);
+		dns_validator_cancel(validator);
+		dns_validator_destroy(&validator);
+	}
+
 	bucketnum = fctx->bucketnum;
 	LOCK(&res->buckets[bucketnum].lock);
 	if (fctx->references == 0)
@@ -3232,7 +3258,9 @@ validated(isc_task_t *task, isc_event_t 
 		add_bad(fctx, &addrinfo->sockaddr, result);
 		isc_event_free(&event);
 		UNLOCK(&fctx->res->buckets[fctx->bucketnum].lock);
-		if (sentresponse)
+		if (!ISC_LIST_EMPTY(fctx->validators))
+			dns_validator_send(ISC_LIST_HEAD(fctx->validators));
+		else if (sentresponse)
 			fctx_done(fctx, result);	/* Locks bucket. */
 		else
 			fctx_try(fctx);			/* Locks bucket. */
@@ -3330,6 +3358,7 @@ validated(isc_task_t *task, isc_event_t 
 		 * be validated.
 		 */
 		UNLOCK(&fctx->res->buckets[fctx->bucketnum].lock);
+		dns_validator_send(ISC_LIST_HEAD(fctx->validators));
 		goto cleanup_event;
 	}
 
@@ -3640,6 +3669,13 @@ cache_name(fetchctx_t *fctx, dns_name_t 
 							   rdataset,
 							   sigrdataset,
 							   valoptions, task);
+					/*
+					 * Defer any further validations.
+					 * This prevents multiple validators
+					 * from manipulating fctx->rmessage
+					 * simultaniously.
+					 */
+					valoptions |= DNS_VALIDATOR_DEFER;
 				}
 			} else if (CHAINING(rdataset)) {
 				if (rdataset->type == dns_rdatatype_cname)
diff -urp bind-9.3.3/lib/dns/validator.c bind-9.3.4/lib/dns/validator.c
--- bind-9.3.3/lib/dns/validator.c	2006-02-27 00:03:52.000000000 +0100
+++ bind-9.3.4/lib/dns/validator.c	2007-01-11 05:51:39.000000000 +0100
@@ -2825,7 +2825,8 @@ dns_validator_create(dns_view_t *view, d
 	ISC_LINK_INIT(val, link);
 	val->magic = VALIDATOR_MAGIC;
 
-	isc_task_send(task, ISC_EVENT_PTR(&event));
+	if ((options & DNS_VALIDATOR_DEFER) == 0)
+		isc_task_send(task, ISC_EVENT_PTR(&event));
 
 	*validatorp = val;
 
@@ -2843,6 +2844,21 @@ dns_validator_create(dns_view_t *view, d
 }
 
 void
+dns_validator_send(dns_validator_t *validator) {
+	isc_event_t *event;
+	REQUIRE(VALID_VALIDATOR(validator));
+
+	LOCK(&validator->lock);
+
+	INSIST((validator->options & DNS_VALIDATOR_DEFER) != 0);
+	event = (isc_event_t *)validator->event;
+	validator->options &= ~DNS_VALIDATOR_DEFER;
+	UNLOCK(&validator->lock);
+
+	isc_task_send(validator->task, ISC_EVENT_PTR(&event));
+}
+
+void
 dns_validator_cancel(dns_validator_t *validator) {
 	REQUIRE(VALID_VALIDATOR(validator));
 
@@ -2856,6 +2872,12 @@ dns_validator_cancel(dns_validator_t *va
 
 		if (validator->subvalidator != NULL)
 			dns_validator_cancel(validator->subvalidator);
+		if ((validator->options & DNS_VALIDATOR_DEFER) != 0) {
+			isc_task_t *task = validator->event->ev_sender;
+			validator->options &= ~DNS_VALIDATOR_DEFER;
+			isc_event_free((isc_event_t **)&validator->event);
+			isc_task_detach(&task);
+		}
 	}
 	UNLOCK(&validator->lock);
 }