CVE-2026-42534

@@ -13,6 +13,9 @@
 	- Fix CVE-2026-41292, Parsing a long list of incoming EDNS options
 	  degrades performance. Thanks to GitHub user 'N0zoM1z0', also Qifan
 	  Zhang from Palo Alto Networks, for the report.
+	- Fix CVE-2026-42534, Jostle logic bypass degrades resolution
+	  performance. Thanks to Qifan Zhang, Palo Alto Networks, for the
+	  report.
 
 23 April 2026: Wouter
 	- Merge #1441: Fix buffer overrun in

@@ -297,12 +297,14 @@ int mesh_make_new_space(struct mesh_area* mesh, sldns_buffer* qbuf)
 	if(mesh->num_reply_states < mesh->max_reply_states)
 		return 1;
 	/* try to kick out a jostle-list item */
-	if(m && m->reply_list && m->list_select == mesh_jostle_list) {
+	if(m && m->list_select == mesh_jostle_list) {
 		/* how old is it? */
 		struct timeval age;
-		timeval_subtract(&age, mesh->env->now_tv,
-			&m->reply_list->start_time);
-		if(timeval_smaller(&mesh->jostle_max, &age)) {
+		if(m->has_first_reply_time)
+			timeval_subtract(&age, mesh->env->now_tv,
+				&m->first_reply_time);
+		if(!m->has_first_reply_time ||
+			timeval_smaller(&mesh->jostle_max, &age)) {
 			/* its a goner */
 			log_nametypeclass(VERB_ALGO, "query jostled out to "
 				"make space for a new one",
@@ -1995,6 +1997,10 @@ int mesh_state_add_reply(struct mesh_state* s, struct edns_data* edns,
 	r->qid = qid;
 	r->qflags = qflags;
 	r->start_time = *s->s.env->now_tv;
+	if(s->reply_list == NULL && !s->has_first_reply_time) {
+		s->first_reply_time = r->start_time;
+		s->has_first_reply_time = 1;
+	}
 	r->next = s->reply_list;
 	r->qname = regional_alloc_init(s->s.region, qinfo->qname,
 		s->s.qinfo.qname_len);

@@ -191,6 +191,12 @@ struct mesh_state {
 	struct module_qstate s;
 	/** the list of replies to clients for the results */
 	struct mesh_reply* reply_list;
+	/** if it has a first reply time */
+	int has_first_reply_time;
+	/** wall-clock time the first client reply was attached;
+	 *  used by mesh_make_new_space() so duplicate retransmits
+	 *  cannot reset jostle aging. */
+	struct timeval first_reply_time;
 	/** the list of callbacks for the results */
 	struct mesh_cb* cb_list;
 	/** set of superstates (that want this state's result)