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 allow unauthenticated Trivial File Transfer Protocol (TFTP) access from the local area network (LAN) as a method to update firmware and to make configuration changes to the device. In conjunction with one of several common vulnerabilities, a remote attacker may be able to gain unauthenticated access as well.
A remote attacker may be able to gain access to the perform TFTP operations. These operations include:
- 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.
Block malicious traffic at your network perimeter
- Packets with a source address of 255.255.255.255
- Packets with a destination port of echo (or other "simple" services)
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.