CVE-2000-0834 in Windows
Summary
by MITRE
The Windows 2000 telnet client attempts to perform NTLM authentication by default, which allows remote attackers to capture and replay the NTLM challenge/response via a telnet:// URL that points to the malicious server, aka the "Windows 2000 Telnet Client NTLM Authentication" vulnerability.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 06/07/2025
The vulnerability described in CVE-2000-0834 represents a critical security flaw in the Windows 2000 telnet client implementation that stems from its default NTLM authentication behavior. This weakness allows remote attackers to exploit the client's automatic authentication mechanism through specially crafted telnet URLs that direct users to malicious servers. The vulnerability specifically targets the Windows 2000 operating system and affects all versions that include the telnet client component, making it particularly dangerous in enterprise environments where legacy systems may still be operational.
The technical flaw manifests when the Windows 2000 telnet client automatically attempts NTLM authentication upon connection to any telnet server. When a user clicks on a malicious telnet:// URL, the client automatically submits NTLM challenge/response credentials to the attacker-controlled server without user intervention or explicit consent. This occurs because the client is configured to default to NTLM authentication, creating an opportunity for credential interception and replay attacks. The vulnerability is classified under CWE-287 which addresses improper authentication, specifically focusing on the lack of proper authentication controls and the automatic submission of credentials.
The operational impact of this vulnerability is significant as it enables attackers to capture valid NTLM challenge/response pairs and subsequently replay them against other systems within the network. This creates a potential for lateral movement and privilege escalation attacks where attackers can gain unauthorized access to network resources. The vulnerability is particularly dangerous because it requires minimal user interaction to exploit, often involving simple URL clicks or automated browser navigation to malicious sites. The attack vector aligns with ATT&CK technique T1075 which covers use of legitimate credentials, and T1566 which covers spearphishing through social engineering.
Mitigation strategies for this vulnerability should focus on immediate operational changes including disabling the telnet client functionality on Windows 2000 systems or implementing strict network segmentation to limit access to telnet services. Organizations should also consider implementing network monitoring to detect unusual authentication patterns and credential capture attempts. The recommended solution involves configuring systems to disable automatic authentication and require explicit user consent before submitting credentials. Additionally, network administrators should ensure that telnet services are not exposed to untrusted networks and that alternative secure authentication methods such as SSH are implemented. This vulnerability demonstrates the importance of proper authentication configuration and the dangers of automatic credential submission in network client applications. The issue highlights fundamental security principles regarding authentication controls and the need for explicit user consent in credential handling processes.