From upstream: https://busybox.net/downloads/fixes-1.25.0/

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>

--- busybox-1.25.0/networking/ntpd.c
+++ busybox-1.25.0-ntpd/networking/ntpd.c
@@ -2051,6 +2051,13 @@ recv_and_process_client_pkt(void /*int f
 		goto bail;
 	}
 
+	/* Respond only to client and symmetric active packets */
+	if ((msg.m_status & MODE_MASK) != MODE_CLIENT
+	 && (msg.m_status & MODE_MASK) != MODE_SYM_ACT
+	) {
+		goto bail;
+	}
+
 	query_status = msg.m_status;
 	query_xmttime = msg.m_xmttime;