CVE-2000-1227 in Windows
Summary
by MITRE
Windows NT 4.0 and Windows 2000 hosts allow remote attackers to cause a denial of service (unavailable connections) by sending multiple SMB SMBnegprots requests but not reading the response that is sent back.
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Analysis
by VulDB Data Team • 10/11/2025
The vulnerability described in CVE-2000-1227 represents a classic denial of service flaw affecting Microsoft Windows NT 4.0 and Windows 2000 operating systems. This weakness stems from the implementation of the Server Message Block protocol which is fundamental to file and printer sharing in Windows networks. The vulnerability specifically targets the SMBnegprots request handling mechanism where the system fails to properly manage connection states when multiple negotiation requests are processed without awaiting appropriate responses. This behavior creates a condition where the server becomes overwhelmed with unprocessed connection attempts, leading to resource exhaustion and ultimately making the system unavailable to legitimate users. The flaw operates at the network protocol level and demonstrates a critical failure in state management within the Windows SMB implementation.
From a technical perspective this vulnerability maps to CWE-400 which defines weaknesses related to resource exhaustion and improper handling of system resources. The flaw exploits the asynchronous nature of SMB protocol negotiations where the server initiates a response but the client fails to read it properly, creating a queue of pending connections that consume system memory and processing resources. The Windows SMB server implementation does not effectively timeout or clean up these pending connections, allowing attackers to continuously send SMBnegprots requests without proper response handling. This creates a resource leak scenario where the server's connection table fills up with incomplete negotiations, preventing new legitimate connections from being established. The vulnerability is particularly dangerous because it requires minimal effort from an attacker to exploit, making it a preferred method for disrupting network services.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromising the availability of critical network resources. When exploited successfully, the affected Windows systems become unavailable to legitimate users attempting to access shared files, printers, or other network resources. The denial of service affects not just individual systems but can cascade through network environments where multiple Windows servers are interconnected. Organizations relying on Windows file sharing services, print services, or other SMB-based functionality face significant operational disruption. The vulnerability is especially problematic in enterprise environments where Windows servers are critical infrastructure components, as it can lead to productivity losses, data access issues, and potential business continuity concerns. Network administrators may observe sudden unavailability of services without clear indications of the underlying cause, complicating troubleshooting efforts.
Mitigation strategies for CVE-2000-1227 should focus on both immediate defensive measures and long-term system hardening. The most direct approach involves applying Microsoft security patches that address the SMB protocol handling issues in Windows NT 4.0 and Windows 2000 systems. Organizations should also implement network-level controls such as firewall rules that limit SMB traffic or restrict the number of concurrent connection attempts from individual hosts. Monitoring systems should be configured to detect unusual patterns of SMBnegprots requests and alert administrators to potential exploitation attempts. Network segmentation can help contain the impact by isolating vulnerable systems from critical network segments. Additionally, implementing proper connection timeout mechanisms and resource limiting on SMB servers can help prevent the accumulation of pending connections. From an ATT&CK framework perspective, this vulnerability aligns with techniques related to service stoppage and resource exhaustion, making it a significant concern for organizations seeking to maintain network availability and prevent disruption attacks.