fix #1916

src/mqtt/MQTT.cpp

@@ -69,7 +69,10 @@ void MQTT::onPublish(char *topic, byte *payload, unsigned int length)
             DEBUG_MSG("Invalid MQTT service envelope, topic %s, len %u!\n", topic, length);
         }
     } else {
-        pb_decode_from_bytes(payload, length, ServiceEnvelope_fields, &e);
+        if (!pb_decode_from_bytes(payload, length, ServiceEnvelope_fields, &e)) {
+            DEBUG_MSG("Invalid MQTT service envelope, topic %s, len %u!\n", topic, length);
+            return;
+        }else {
             if (strcmp(e.gateway_id, owner.id) == 0)
                 DEBUG_MSG("Ignoring downlink message we originally sent.\n");
             else {
@@ -84,7 +87,7 @@ void MQTT::onPublish(char *topic, byte *payload, unsigned int length)
                         packetPool.release(p);
                 }
             }
-
+        }
         // make sure to free both strings and the MeshPacket (passing in NULL is acceptable)
         free(e.channel_id);
         free(e.gateway_id);