CVE-2001-0006 in Windows
Summary
by MITRE
The Winsock2ProtocolCatalogMutex mutex in Windows NT 4.0 has inappropriate Everyone/Full Control permissions, which allows local users to modify the permissions to "No Access" and disable Winsock network connectivity to cause a denial of service, aka the "Winsock Mutex" vulnerability.
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Analysis
by VulDB Data Team • 10/11/2025
The CVE-2001-0006 vulnerability represents a critical access control flaw in the Windows NT 4.0 operating system that specifically targets the Winsock2 Protocol Catalog Mutex mechanism. This vulnerability resides within the core networking infrastructure of the operating system, where the mutex object controlling Winsock protocol catalog access has been improperly configured with overly permissive permissions. The mutex in question is designed to coordinate access to the Windows Sockets (Winsock) protocol catalog, which manages the registration and access to various network protocol providers that enable applications to communicate over networks. The flaw stems from the default configuration where the mutex is created with Everyone group having Full Control permissions, creating an exploitable path for local users to manipulate system-level networking components.
The technical exploitation of this vulnerability occurs through a straightforward yet effective method that leverages the local user's ability to modify object permissions within the Windows security model. An attacker with local access can simply modify the mutex permissions to remove the necessary access rights for the Winsock service, effectively disabling network connectivity for the entire system. This permission modification process directly violates the principle of least privilege and demonstrates a fundamental flaw in the Windows NT 4.0 security architecture. The mutex object serves as a synchronization primitive that prevents multiple processes from simultaneously modifying the protocol catalog, but its overly permissive default settings create a vector for privilege escalation and denial of service attacks. This vulnerability specifically aligns with CWE-276, which addresses improper permissions for critical resources, and represents a classic case of insecure default configurations in operating system components.
The operational impact of CVE-2001-0006 extends beyond simple denial of service to potentially compromise the entire network functionality of affected systems. When local users successfully modify the mutex permissions to "No Access," they effectively disable the Winsock networking stack, which impacts all network-dependent applications and services running on the system. This vulnerability is particularly dangerous because it operates at the kernel level and affects the fundamental networking capabilities that many enterprise applications depend upon. The attack vector requires only local system access, making it accessible to users who may have legitimate access to the system but lack administrative privileges. From an attacker's perspective, this represents a low-effort, high-impact method of disrupting network services and can be particularly effective in environments where multiple users have local access to critical servers. The vulnerability also enables indirect privilege escalation scenarios where an attacker might use the network disruption to cover other malicious activities or to force system administrators into making security compromises during incident response.
Mitigation strategies for this vulnerability focus primarily on immediate permission adjustments and long-term system hardening measures. System administrators should immediately modify the mutex permissions to restrict access to only the necessary system components and users, typically requiring administrative privileges to perform such modifications. The recommended approach involves removing the Everyone group's Full Control permissions and implementing more restrictive access controls that align with the principle of least privilege. Additionally, organizations should implement comprehensive patch management programs to ensure all Windows NT 4.0 systems are updated with the appropriate security patches released by Microsoft. The vulnerability also highlights the importance of regular security audits and permission reviews to identify and remediate similar insecure default configurations across the enterprise. From an ATT&CK framework perspective, this vulnerability maps to T1486 (Data Encrypted for Impact) and T1566 (Phishing) as attackers might use this vulnerability to disrupt network services during broader attack campaigns, and to T1078 (Valid Accounts) since the attack requires only local access to exploit the privilege escalation potential. Organizations should also consider implementing network monitoring solutions to detect unusual permission changes and unauthorized modifications to critical system objects that could indicate exploitation attempts.