Huawei USG5500 with software V300R001C00 and V300R001C00 allows attackers to bypass the anti-DDoS module of the USGs to cause a denial of service condition on the backend server.
http://www.securityfocus.com/bid/93891
http://www.huawei.com/en/psirt/security-advisories/huawei-sa-20161026-01-usg-en