CVE-2000-0347 in Windows
Summary
by MITRE
Windows 95 and Windows 98 allow a remote attacker to cause a denial of service via a NetBIOS session request packet with a NULL source name.
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Analysis
by VulDB Data Team • 06/02/2025
The vulnerability described in CVE-2000-0347 represents a classic denial of service flaw affecting Microsoft Windows 95 and Windows 98 operating systems. This weakness specifically targets the NetBIOS session service implementation within these legacy platforms, where the system fails to properly validate incoming session request packets. The vulnerability arises when a remote attacker crafts a malicious NetBIOS session request packet containing a NULL source name field, which the affected systems process without adequate sanitization or error handling mechanisms. This particular flaw demonstrates a fundamental lack of input validation in the network protocol stack, allowing malicious actors to exploit the system's failure to reject malformed packets.
The technical execution of this vulnerability relies on the inherent design weakness in how Windows 95 and Windows 98 handle NetBIOS session establishment requests. When the operating system receives a session request packet with a NULL source name, the system's session management component enters an undefined state where it cannot properly process or reject the malformed request. This condition causes the NetBIOS service to become unresponsive or crash entirely, resulting in a complete denial of service for network file and printer sharing capabilities. The flaw exists at the protocol level rather than at the application layer, making it particularly effective as a system-wide disruption mechanism. The vulnerability is categorized under CWE-20 as "Improper Input Validation" and aligns with ATT&CK technique T1499.004 for "Network Denial of Service" within the context of service disruption attacks.
The operational impact of CVE-2000-0347 extends beyond simple service interruption, as it affects the core networking functionality that many users relied upon for file sharing, printer access, and network communication in the pre-Windows 2000 era. Organizations running these legacy systems would experience complete network service outages, potentially affecting productivity and business operations significantly. The vulnerability is particularly dangerous in corporate environments where Windows 95 and 98 systems might still be in use for legacy applications, as attackers could systematically disrupt network operations without requiring authentication or advanced privileges. The lack of proper error handling in the NetBIOS subsystem creates a persistent threat vector that can be exploited repeatedly, making it a preferred target for denial of service attacks against older network infrastructures.
Mitigation strategies for this vulnerability focus primarily on network segmentation and access control measures rather than patching, since Microsoft officially discontinued support for Windows 95 and 98 long before this vulnerability was widely recognized. Network administrators should implement firewall rules to block NetBIOS traffic at the network perimeter, particularly TCP and UDP ports 139 and 445 that are commonly used for NetBIOS services. The most effective long-term solution involves migrating away from these unsupported operating systems to modern platforms that receive regular security updates and have robust input validation mechanisms. Additionally, implementing network monitoring to detect unusual NetBIOS traffic patterns can help identify exploitation attempts. Organizations maintaining legacy systems should consider disabling NetBIOS entirely when possible, as many applications can function without this protocol, thereby eliminating the attack surface entirely. The vulnerability serves as a historical example of how insufficient input validation in network protocols can create systemic security weaknesses that persist across multiple versions of software platforms.