CVE-2015-7259
ZTE ADSL ZXV10 W300 modems W300V2.1.0f_ER7_PE_O57 and W300V2.1.0h_ER7_PE_O57 allow user accounts to have multiple valid username and password pairs, which allows remote authenticated users to login to a target account via any of its username and password pairs.
Source: CVE-2015-7259