CVE-2000-1217 in Windows
Summary
by MITRE
Microsoft Windows 2000 before Service Pack 2 (SP2), when running in a non-Windows 2000 domain and using NTLM authentication, and when credentials of an account are locally cached, allows local users to bypass account lockout policies and make an unlimited number of login attempts, aka the "Domain Account Lockout" vulnerability.
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Analysis
by VulDB Data Team • 12/30/2024
This vulnerability resides in the authentication mechanisms of Microsoft Windows 2000 operating systems prior to Service Pack 2, specifically affecting systems operating in non-Windows 2000 domain environments. The flaw exploits the interaction between NTLM authentication protocols and local credential caching mechanisms, creating a significant security weakness that undermines fundamental account protection measures. The vulnerability manifests when Windows 2000 systems cache user credentials locally and subsequently authenticate against non-Windows 2000 domains, enabling malicious actors to circumvent the account lockout policy that normally prevents brute force attacks through repeated authentication attempts.
The technical root cause stems from how Windows 2000 handles NTLM authentication in mixed domain environments where the system operates outside of native Windows 2000 domain controllers. When credentials are locally cached, the system fails to properly enforce account lockout thresholds during authentication attempts, allowing unlimited login attempts without triggering the expected security mechanisms. This occurs because the local authentication process bypasses the domain controller's account lockout enforcement, creating a path where attackers can repeatedly attempt to authenticate with various credential combinations without facing the normal account lockout consequences. The vulnerability specifically affects systems where the local security authority (LSA) cache stores user credentials and performs authentication against external domains that do not enforce the same lockout policies as Windows 2000 native domains.
The operational impact of this vulnerability is substantial as it fundamentally compromises the integrity of account security measures within affected Windows 2000 environments. Attackers can leverage this weakness to perform unlimited brute force attacks against cached user accounts, potentially leading to unauthorized access to sensitive systems and data. The vulnerability undermines the effectiveness of basic security controls such as account lockout policies, which are designed to prevent automated credential guessing attacks and protect against dictionary attacks. Organizations running Windows 2000 systems in non-native domain environments face increased risk of credential compromise, particularly in scenarios where local caching is enabled and users authenticate against external authentication sources.
Mitigation strategies for this vulnerability require immediate implementation of service pack updates, specifically Microsoft Windows 2000 Service Pack 2, which addresses the underlying authentication flaw in the LSA and credential caching mechanisms. System administrators should disable local credential caching where possible, particularly in environments where authentication occurs against non-Windows 2000 domains, as this eliminates the attack vector entirely. Network segmentation and access controls should be implemented to limit local user access to systems that cache credentials, while monitoring should be enhanced to detect unusual authentication patterns that may indicate exploitation attempts. Additionally, organizations should consider implementing supplementary authentication controls such as two-factor authentication and enhanced monitoring of authentication logs to detect potential abuse of this vulnerability. This vulnerability maps to CWE-307, which addresses improper restriction of excessive authentication attempts, and aligns with ATT&CK technique T1110 for Brute Force attacks, representing a critical weakness in authentication security that requires immediate remediation.
This vulnerability demonstrates the complexity of authentication security in mixed domain environments and highlights the importance of proper service pack management in maintaining system security. The flaw represents a fundamental design weakness in how Windows 2000 handled cross-domain authentication with local caching, creating a persistent security gap that could be exploited by attackers with local system access. Organizations should recognize this as a critical vulnerability requiring immediate attention, as it effectively neutralizes account lockout protections and enables unlimited authentication attempts against cached credentials. The security implications extend beyond simple credential compromise to potentially enable broader system access and data exfiltration in environments where local access is possible.