The web interface for the Arris / Motorola Surfboard SBG6580 has several vulnerabilities that, when combined, allow an arbitrary website to take control of the modem, even if the user is not currently logged in. The attacker must successfully know, or guess, the targets internal gateway IP address. This is usually a default value of 192.168.0.1. First, a hardcoded backdoor account was discovered in the source code of one device with the credentials "technician/yZgO8Bvj". Due to lack of CSRF in the devices login form, these credentials - along with the default "admin/motorola" - can be sent to the device by an arbitrary website, thus inadvertently logging the user into the router. Once successfully logged in, a persistent XSS vulnerability is exploited in the firewall configuration page. This allows injection of Javascript that can perform any available action in the router interface. The following firmware versions have been tested as vulnerable: SBG6580-6.5.2.0-GA-06-077-NOSH, and SBG6580-8.6.1.0-GA-04-098-NOSH.
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