D-Link DIR-2640 HNAP PrivateLogin Authentication Bypass Vulnerability. This vulnerability allows network-adjacent attackers to bypass authentication on affected installations of D-Link DIR-2640 routers. Authentication is not required to exploit this vulnerability.
The specific flaw exists within the web management interface, which listens on TCP port 80 by default. A crafted XML element in the login request can cause authentication to succeed without providing proper credentials. An attacker can leverage this vulnerability to bypass authentication on the system. Was ZDI-CAN-19545.
The requirements for the product dictate the use of an established authentication algorithm, but the implementation of the algorithm is incorrect.