CVE-2001-0348 in Windows
Summary
by MITRE
Microsoft Windows 2000 telnet service allows attackers to cause a denial of service (crash) via a long logon command that contains a backspace.
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Analysis
by VulDB Data Team • 10/06/2025
The vulnerability described in CVE-2001-0348 represents a classic buffer overflow condition within the telnet service component of Microsoft Windows 2000 operating systems. This issue specifically affects the authentication handling mechanism of the telnet service when processing logon commands that contain excessive backspace characters. The flaw exists in the way the telnet service processes input strings during the authentication phase, creating a scenario where malformed input can trigger unexpected behavior in the underlying software components. The vulnerability demonstrates a fundamental lack of proper input validation and boundary checking within the telnet service implementation, allowing malicious actors to exploit the service through carefully crafted command sequences that exceed predetermined buffer limits.
The technical exploitation of this vulnerability occurs when an attacker sends a specially constructed logon command containing an excessive number of backspace characters to the telnet service. These backspace characters, when processed by the service, cause the internal string handling routines to manipulate memory locations beyond their allocated boundaries. The backspace character sequence effectively creates a situation where the telnet service's input buffer management becomes corrupted, leading to memory pointer manipulation that ultimately results in service termination. This type of vulnerability falls under the category of buffer overflow conditions that are commonly classified as CWE-121, which specifically addresses stack-based buffer overflow vulnerabilities. The exploitation process leverages the service's failure to properly validate input length and character sequences during authentication, creating a path for arbitrary code execution or service disruption.
The operational impact of CVE-2001-0348 extends beyond simple service disruption to represent a broader security concern for systems running vulnerable telnet services. When exploited successfully, this vulnerability can cause the telnet service to crash and restart, effectively creating a denial of service condition that prevents legitimate users from accessing system resources through telnet connections. The vulnerability is particularly concerning because it affects a widely used remote access protocol that was commonly enabled on Windows 2000 systems, making the attack surface extensive across enterprise networks. Network administrators and system operators who had telnet services enabled were particularly vulnerable to this attack vector, as it required minimal technical expertise to execute and could be automated through simple scripts. The vulnerability's impact aligns with the MITRE ATT&CK framework's privilege escalation and denial of service tactics, where adversaries can leverage service weaknesses to disrupt operations and potentially gain further access to network resources.
Mitigation strategies for this vulnerability should focus on immediate service hardening and long-term architectural improvements. The most effective immediate response involves disabling the telnet service entirely on affected systems, as telnet represents an inherently insecure protocol that lacks encryption and proper authentication mechanisms. System administrators should implement network segmentation and access controls to limit exposure of telnet services to trusted networks only. Additionally, applying Microsoft security patches and updates that address the specific buffer overflow conditions in the telnet service implementation provides the most comprehensive protection. Organizations should also consider implementing network monitoring solutions that can detect anomalous telnet traffic patterns and potential exploitation attempts. The vulnerability highlights the importance of proper input validation and boundary checking in service implementations, with recommendations that align with secure coding practices outlined in industry standards such as the OWASP Secure Coding Practices and the CERT/CC secure coding guidelines. Regular security assessments and vulnerability scanning should be implemented to identify and remediate similar issues in other network services and applications.