The San Diego Supercomputer Center (SDSC) has recently discovered several vulnerabilities in the Alcatel Speed Touch line of Asymmetric Digital Subscriber Line (ADSL) modems. These vulnerabilities are the result of weak authentication and access control policies and result in one or more of the following impacts: unauthorized access, unauthorized monitoring, information leakage, denial of service, and permanent disability of affected devices.
The SDSC has published additional information regarding these vulnerabilities at http://security.sdsc.edu/self-help/alcatel/.
Alcatel ADSL modems contain a special account (EXPERT) for gaining privileged access to the device. This account is secured via a challenge-response password authentication mechanism. While the use of such a mechanism is commendable, the algorithm used is not sufficiently strong. Attackers who know the algorithm used to compute the response can compute the correct response using information given to them during the login process.
Attackers who are able to connect to the ADSL modem can enter a predictable userid and password to gain privileged access to the device. This access can be used to reconfigure the device, potentially introducing additional security weaknesses.
The CERT/CC is currently unaware of a practical solution to this problem.
The CERT Coordination Center would like to thank Tom Perrine and Tsutomu Shimomura of the San Diego Supercomputer Center for notifying us about this problem and their help in constructing this advisory.
This document is based on research by the SDSC and was written by Cory Cohen and Jeffrey P. Lanza.