- Fix CVE-2026-50251, Attacker supplied 0.0.0.0/:: glue triggers

defensive full-cache flush. Thanks to Qifan Zhang, Palo Alto
  Networks, for the report.

doc/unbound.conf.rst

@@ -2055,6 +2055,13 @@ These options are part of the ``server:`` section.
     flushing away any poison.
     A value of 10 million is suggested.
 
+    It is useful to add 0.0.0.0/8 and '::' to the
+    :ref:`do-not-query-address<unbound.conf.do-not-query-address>` list.
+    Otherwise they may be answered, from localhost, and the different source
+    makes an unwanted reply that unnecessarily ticks up.
+    The :ref:`do-not-query-localhost<unbound.conf.do-not-query-localhost>`
+    option includes them, the zero subnets, when it is enabled.
+
     Default: 0 (disabled)
 
 

iterator/iter_donotq.c

@@ -132,6 +132,18 @@ donotq_apply_cfg(struct iter_donotq* dq, struct config_file* cfg)
 		if(cfg->do_ip6) {
 			if(!donotq_str_cfg(dq, "::1"))
 				return 0;
+			if(!donotq_str_cfg(dq, "::ffff:127.0.0.0/104"))
+				return 0;
+		}
+		/* RFC 1122 3.2.1.3 / RFC 6890 / RFC 4291 2.5.2: not valid as
+		 * destination; on Linux these route to the local host. */
+		if(!donotq_str_cfg(dq, "0.0.0.0/8"))
+			return 0;
+		if(cfg->do_ip6) {
+			if(!donotq_str_cfg(dq, "::"))
+				return 0;
+			if(!donotq_str_cfg(dq, "::ffff:0:0/96"))
+				return 0;
 		}
 	}
 	addr_tree_init_parents(&dq->tree);

testdata/dns_error_reporting.rpl

@@ -12,6 +12,7 @@ server:
 	ede: no  # It is not needed for dns-error-reporting; only for clients to receive EDEs
 	dns-error-reporting: yes
 	do-ip6: no
+	do-not-query-localhost: no
 
 stub-zone:
 	name: domain