The web-based configuration interface for the Cisco ATA 186 Analog Telephone Adaptor allows remote attackers to bypass authentication via an HTTP POST request with a single byte, which allows the attackers to (1) obtain the password from the login screen, or (2) reconfigure the adaptor by modifying certain request parameters.
http://www.securityfocus.com/bid/4712
http://www.iss.net/security_center/static/9057.php
http://www.iss.net/security_center/static/9056.php
http://www.cisco.com/warp/public/707/ata186-password-disclosure.shtml
http://archives.neohapsis.com/archives/bugtraq/2002-05/0083.html