Microsoft Windows ME Security Patch: 'HyperTerminal Buffer Overflow' Vulnerability

The HyperTerminal application is a utility that installs, by default, on all versions of Windows 98, 98SE, Windows ME, Windows NT, and Windows 2000. The product contains an unchecked buffer in a section of the code that processes Telnet URLs. If a user opened an HTML mail that contained a particularly malformed Telnet URL, it would result in a buffer overrun that could enable the creator of the mail to cause arbitrary code to run on the user’s system. HyperTerminal is the default Telnet client on Windows 98, 98SE and ME. However, it is not the default Telnet client on Windows 2000, and Windows 2000 users who have not taken steps to make it the default Telnet client would not be affected by the vulnerability. (Windows NT4.0 is not affected by this vulnerability. The HyperTerminal client that ships with Windows NT4 does not include a TCP/IP connection method. As such, the NT4 HyperTerminal client cannot be setup as the default telnet client, and would not launch in response to a supplied Telnet URL.)