ZTE E8810/E8820/E8822 series routers have an MQTT DoS vulnerability, which is caused by the failure of the device to verify the validity of abnormal messages. A remote attacker could connect to the MQTT server and send an MQTT exception message to the specified device, which will cause the device to deny service. This affects:<ZXHN E8810, ZXHN E8820, ZXHN E8822><E8810 V1.0.26, E8810 V2.0.1, E8820 V1.1.3L, E8820 V2.0.13, E8822 V2.0.13>