CVE-2000-0673 in Windows
Summary
by MITRE
The NetBIOS Name Server (NBNS) protocol does not perform authentication, which allows remote attackers to cause a denial of service by sending a spoofed Name Conflict or Name Release datagram, aka the "NetBIOS Name Server Protocol Spoofing" vulnerability.
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Analysis
by VulDB Data Team • 10/13/2025
The CVE-2000-0673 vulnerability represents a critical weakness in the NetBIOS Name Server protocol that fundamentally lacks authentication mechanisms, creating a significant security gap in network infrastructure. This vulnerability specifically affects the NBNS protocol implementation in Microsoft Windows systems and other platforms that utilize NetBIOS naming services. The flaw resides in the protocol's design where name resolution requests and responses are accepted without verifying the authenticity of the sending entity, making it susceptible to various forms of malicious interference. The vulnerability is categorized under CWE-287 which addresses improper authentication issues, and aligns with ATT&CK technique T1133 which covers external remote services and network service scanning. This weakness allows attackers to exploit the absence of cryptographic verification or identity validation in the name server protocol, enabling unauthorized entities to manipulate network naming services through forged network packets.
The technical implementation of this vulnerability stems from the inherent design flaw in the NetBIOS Name Server protocol where it accepts name conflict and name release datagrams without validating the source address or requiring any form of authentication. Attackers can exploit this by crafting and transmitting spoofed datagrams that appear to originate from legitimate network hosts. When the target system processes these forged messages, it may incorrectly update its local name tables or initiate inappropriate network behavior. The protocol's lack of integrity checks means that any host can send a name conflict message claiming that a particular NetBIOS name is already in use, or send a name release message indicating that a name should be removed from the network. This creates a scenario where legitimate network services can be disrupted or compromised simply through the injection of maliciously crafted network traffic that mimics legitimate protocol behavior.
The operational impact of CVE-2000-0673 extends beyond simple denial of service conditions to potentially compromise entire network naming services and create cascading effects throughout the infrastructure. When an attacker successfully spoofs a name conflict message, the target system may remove legitimate name registrations from its cache, effectively causing network services that depend on those names to become unavailable. The vulnerability can be particularly damaging in corporate environments where network naming services are critical for file sharing, printer services, and other network operations. The attack can be executed remotely without requiring any special privileges or access to the target system, making it an attractive vector for malicious actors. This weakness enables attackers to perform network reconnaissance by identifying which systems are running NetBIOS services and potentially disrupt critical business operations through sustained denial of service attacks that target core naming services. The vulnerability also contributes to broader network instability by causing name resolution failures that can propagate throughout the network infrastructure.
Mitigation strategies for CVE-2000-0673 require a multi-layered approach addressing both network-level protections and system-level configurations. Organizations should implement network segmentation and access control measures to limit exposure of NetBIOS services to trusted networks only, while disabling unnecessary NetBIOS services on systems that do not require them. Network administrators should consider deploying firewalls and access control lists that filter traffic on NetBIOS ports 137 and 138, preventing unauthorized access to name server services. The most effective long-term solution involves transitioning away from legacy NetBIOS protocols to more secure modern alternatives such as DNS-based name resolution or implementing SMBv2/v3 protocols that include proper authentication mechanisms. System administrators should also consider implementing network monitoring tools that can detect and alert on suspicious name conflict or release messages that deviate from expected network behavior patterns. Additionally, regular security assessments should verify that NetBIOS services are properly configured and that appropriate network segmentation is in place to minimize the attack surface. The vulnerability demonstrates the importance of implementing proper authentication and integrity checks in network protocols, as outlined in security frameworks such as NIST SP 800-53 and ISO 27001 standards for secure network configuration and access control.