CVE-2000-0581 in Windows
Summary
by MITRE
Windows 2000 Telnet Server allows remote attackers to cause a denial of service by sending a continuous stream of binary zeros, which causes the server to crash.
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Analysis
by VulDB Data Team • 02/23/2025
The vulnerability identified as CVE-2000-0581 represents a critical denial of service weakness in the Windows 2000 Telnet Server implementation. This flaw manifests when remote attackers exploit the server's handling of input data by transmitting continuous streams of binary zeros, effectively triggering a system crash that renders the telnet service unavailable to legitimate users. The vulnerability specifically targets the protocol handling mechanisms within the telnet server component, which fails to properly validate or process malformed input sequences.
From a technical perspective, the flaw stems from inadequate input validation within the telnet server's data processing routines. When the server receives a continuous stream of null bytes, its internal parsing logic becomes overwhelmed or enters an undefined state that leads to system instability and eventual crash. This type of vulnerability falls under the CWE-129 weakness category, which encompasses issues related to improper validation of input boundaries and handling of malformed data. The vulnerability demonstrates a classic example of insufficient error handling in network services where the server does not properly account for edge cases in data transmission.
The operational impact of this vulnerability extends beyond simple service disruption, as it enables attackers to exploit the Windows 2000 Telnet Server with minimal technical expertise. The attack requires only the ability to establish a telnet connection to the target system and send a continuous stream of null bytes, making it particularly dangerous in environments where telnet services are exposed to untrusted networks. This vulnerability directly aligns with ATT&CK technique T1499.004, which covers network denial of service attacks targeting remote services. The impact can be significant for organizations relying on telnet for administrative access, as the service disruption can affect system management capabilities and potentially provide attackers with opportunities for further exploitation.
Organizations should implement immediate mitigations including disabling unnecessary telnet services, restricting access through firewall rules, and applying available security patches from Microsoft. The vulnerability highlights the importance of input validation and proper error handling in network services, particularly those handling untrusted data from remote sources. Security monitoring should include detection of unusual connection patterns and data transmission behaviors that may indicate exploitation attempts. Additionally, organizations should consider implementing network segmentation to limit exposure of critical systems to potential attackers and establish robust incident response procedures for handling denial of service incidents. The vulnerability serves as a reminder of the critical need for proper protocol implementation and validation in server-side applications to prevent simple input manipulation from causing system-wide failures.