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/.
To allow your ISP to upgrade the firmware of the ADSL modem remotely, unauthenticated TFTP access is provided to users with physical access to the wire on the WAN side of the modem. While this access is normally used legitimately by your ISP, it could also be abused by an attacker with physical access to the wire outside of your home or at a local access point.
An attacker with physical access to your wire may be able to gain unauthenticated TFTP access, allowing them to perform the following operations:
- recovery and setting of passwords
- inspection and updates to the firmware
- destructive updates to the firmware
- malicious custom updates to the firmware
Note that affected Alcatel ADSL modems do not provide any mechanism for determining the validity of firmware updates, so a remote attacker may be able to install custom firmware that operated as a DDoS client or a network sniffer. Similarly, an attacker could produce an invalid firmware revision that would disable the device completely, leaving victims no alternative but to return the disabled unit to the manufacturer.
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.