Vulnerability Note VU#243592

Alcatel ADSL modems provide EXPERT administrative account with an easily reversible encrypted password

Overview

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/.

I. Description

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.

Because the EXPERT account is accessible via TELNET, HTTP, and FTP, the ADSL modem must have an IP address that is accessible from the Internet to exploit this vulnerability. Alcatel ADSL products do not enable this feature over the wide area network (WAN) interface by default. Note, however, that an attacker with TFTP access may be able to reconfigure the device to enable this feature.

This authentication mechanism is present even if the user has set a user supplied password.

Any problem or vulnerability on your internal network that allows an intruder to communicate with the modem may lead to its compromise, including Trojan horses, compromised systems, or other "bounce" vulnerabilities like the FTP bounce vulnerability described in

http://www.cert.org/tech_tips/ftp_port_attacks.html

II. Impact

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.

III. Solution

The CERT/CC is currently unaware of a practical solution to this problem.

Systems Affected

Vendor	Status	Date Notified	Date Updated
Alcatel	Vulnerable	10-Apr-2001

References

http://security.sdsc.edu/self-help/alcatel/
http://www.alcatel.com/consumer/dsl/security.htm
http://www.securityfocus.com/bid/2568

Credit

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.

Other Information

Date Public:	2001-04-10
Date First Published:	2001-04-10
Date Last Updated:	2001-09-14
CERT Advisory:	CA-2001-08
CVE-ID(s):
NVD-ID(s):
US-CERT Technical Alerts:
Metric:	27.56
Document Revision:	15

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