CVE-1999-0505 is a vulnerability related to Windows NT domain user or administrator accounts having guessable passwords. This vulnerability arises from weak password policies or poor password management practices that allow attackers to guess or brute-force credentials for domain accounts. Since domain accounts, especially administrator accounts, have elevated privileges within a Windows NT or Windows 2000 domain environment, compromising such accounts can lead to full control over the domain, including access to sensitive data, ability to create or delete user accounts, and control over domain resources. The CVSS score of 7.2 (high severity) reflects the significant impact on confidentiality, integrity, and availability if exploited. The vector AV:L (local attack) indicates that the attacker must have local access to the system or network to attempt password guessing, but no authentication is required (Au:N), meaning the attacker can try to guess passwords without prior credentials. The vulnerability does not have an official patch, as it is fundamentally a weakness in password strength rather than a software flaw. No known exploits in the wild have been reported, but the risk remains high due to the critical nature of domain accounts and the ease with which weak passwords can be guessed or cracked using common tools. This vulnerability is specific to legacy Microsoft operating systems such as Windows NT and Windows 2000, which are now largely obsolete but may still be in use in some legacy environments.

For European organizations, the impact of this vulnerability can be severe if legacy Windows NT or Windows 2000 domain controllers or systems are still in operation. Compromise of domain user or administrator accounts can lead to unauthorized access to corporate networks, data breaches, disruption of services, and potential lateral movement within the network. Confidentiality is at risk as attackers can access sensitive information; integrity is compromised as attackers can modify or delete data; and availability can be affected if attackers disrupt domain services or lock out legitimate users. Although modern environments have largely replaced these legacy systems, some critical infrastructure, industrial control systems, or specialized legacy applications in Europe might still rely on them, increasing risk. Additionally, organizations with poor password policies or insufficient network segmentation are more vulnerable. The lack of patches means organizations must rely on administrative controls and password management to mitigate risk.

1. Immediate audit of all Windows NT and Windows 2000 domain user and administrator accounts to identify weak or guessable passwords. 2. Enforce strong password policies requiring complex, lengthy passwords that resist guessing and brute-force attacks. 3. Implement account lockout policies to limit the number of failed login attempts and slow down brute-force attacks. 4. Where possible, upgrade legacy Windows NT/2000 domain controllers and systems to supported, modern Windows Server versions with enhanced security features. 5. Use network segmentation and restrict local access to domain controllers to trusted personnel only, minimizing the attack surface. 6. Employ multi-factor authentication (MFA) for domain administrator accounts to add an additional layer of security beyond passwords. 7. Regularly monitor and review domain account activities and logs for suspicious login attempts or anomalies. 8. Educate administrators and users about the risks of weak passwords and the importance of secure credential management. 9. If legacy systems cannot be upgraded immediately, consider isolating them from critical network segments and restrict their network exposure.