An issue was discovered on D-Link DSL-2640B B2 EU_4.01B devices. A hard-coded account allows management-interface login with high privileges. The logged-in user can perform critical tasks and take full control of the device.

An issue was discovered on D-Link DSL-2640B B2 EU_4.01B devices. The device can be reset to its default configuration by accessing an unauthenticated URL.

An issue was discovered on D-Link DSL-2640B B2 EU_4.01B devices. Authentication can be bypassed when accessing cgi modules. This allows one to perform administrative tasks (e.g., modify the admin password) with no authentication.

An issue was discovered on D-Link DSL-2640B B2 EU_4.01B devices. The function do_cgi(), which processes cgi requests supplied to the device's web servers, is vulnerable to a remotely exploitable stack-based buffer overflow. Unauthenticated exploitation is possible by combining this vulnerability with CVE-2020-9277.

An issue was discovered on D-Link DSL-2640B B2 EU_4.01B devices. A cfm UDP service listening on port 65002 allows remote, unauthenticated exfiltration of administrative credentials.

Cross-site request forgery (CSRF) vulnerability in redpass.cgi in D-Link DSL-2640B Firmware EU_4.00 allows remote attackers to hijack the authentication of administrators for requests that change the administrator password via the sysPassword parameter.