CVE-2000-0403 in Windows
Summary
by MITRE
The CIFS Computer Browser service on Windows NT 4.0 allows a remote attacker to cause a denial of service by sending a large number of host announcement requests to the master browse tables, aka the "HostAnnouncement Flooding" or "HostAnnouncement Frame" vulnerability.
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Analysis
by VulDB Data Team • 04/21/2026
The CVE-2000-0403 vulnerability represents a significant denial of service weakness in the Server Message Block protocol implementation within Windows NT 4.0 systems. This flaw specifically targets the Computer Browser service that maintains master browse tables for network discovery and browsing operations. The vulnerability operates through a sophisticated attack vector that leverages the inherent design of the CIFS protocol's host announcement mechanism, creating a scenario where legitimate network operations become impossible due to resource exhaustion. The attack exploits the fundamental architecture of Windows NT 4.0's network browsing infrastructure, which relies on periodic host announcements to maintain accurate browse lists across the network.
The technical implementation of this vulnerability stems from the lack of proper input validation and rate limiting within the Computer Browser service's handling of host announcement requests. When a remote attacker sends an excessive number of malformed or duplicate host announcement frames to a target system, the service becomes overwhelmed with processing requests that should be simple network discovery operations. The flaw manifests as the service's inability to properly filter or throttle these requests, leading to a cascade of resource consumption that ultimately results in the complete unavailability of the browsing service. This behavior aligns with CWE-400, which classifies the vulnerability as a resource exhaustion issue where the system's capacity to handle legitimate requests is consumed by malicious traffic patterns.
The operational impact of CVE-2000-0403 extends far beyond simple service disruption, as it fundamentally compromises network accessibility and user productivity within affected environments. When the master browse tables become flooded with malicious announcements, network users experience complete inability to discover shared resources, browse network drives, or access printers and other networked devices. The vulnerability affects the core network discovery infrastructure that Windows NT 4.0 relies upon for proper network operation, creating a cascading failure that can impact entire organizational networks. Organizations using Windows NT 4.0 servers as domain controllers or file servers face particularly severe consequences, as the vulnerability can render critical network services inaccessible and potentially impact authentication and authorization processes that depend on network browsing.
This vulnerability demonstrates the importance of implementing proper network security controls and service hardening measures for legacy systems. The attack pattern represents a classic example of a protocol-based denial of service that exploits the inherent design assumptions of network services. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, which covers network denial of service attacks, and T1595.001, which involves network scanning and enumeration techniques. Organizations should implement network segmentation to isolate critical services, deploy rate limiting mechanisms at network boundaries, and ensure that legacy systems are properly patched or isolated from critical network segments. The vulnerability also highlights the necessity of monitoring network traffic for unusual patterns of broadcast traffic and implementing proper access controls to limit which systems can send broadcast announcements to master browse servers.
The remediation approach for CVE-2000-0403 requires a multi-layered strategy that addresses both immediate protection and long-term system security. Immediate mitigation involves disabling the Computer Browser service on affected systems when not strictly necessary, implementing network access controls to limit broadcast traffic, and applying available security patches from Microsoft. However, given that Windows NT 4.0 reached end-of-life years ago, organizations must consider more comprehensive solutions including system migration to supported platforms, network segmentation strategies, and proper network monitoring to detect similar attack patterns. The vulnerability serves as a historical example of how protocol-level design flaws can create persistent security challenges and emphasizes the critical importance of maintaining current security practices and system updates to prevent exploitation of known vulnerabilities.