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.
CWE-287 - Improper Authentication
Improper (or broken) authentication attacks are widespread, and have accounted for many of the worst data breaches in recent years. Improper authentication attacks are a class of vulnerabilities where an attacker impersonates a legitimate user by exploiting weaknesses in either session management or credential management to gain access to the user’s account. This can result in disclosure of sensitive information, and can lead to system compromise, theft, identity theft, and fraud.