A vulnerability in the external authentication mechanism of Cisco Modeling Labs could allow an unauthenticated, remote attacker to access the web interface with administrative privileges. This vulnerability is due to the improper handling of certain messages that are returned by the associated external authentication server. An attacker could exploit this vulnerability by logging in to the web interface of an affected server. Under certain conditions, the authentication mechanism would be bypassed and the attacker would be logged in as an administrator. A successful exploit could allow the attacker to obtain administrative privileges on the web interface of an affected server, including the ability to access and modify every simulation and all user-created data. To exploit this vulnerability, the attacker would need valid user credentials that are stored on the associated external authentication server. Cisco has released software updates that address this vulnerability. There are workarounds that address this vulnerability.
The authentication algorithm is sound, but the implemented mechanism can be bypassed as the result of a separate weakness that is primary to the authentication error.