CVE-2002-0054 in Windows
Summary
by MITRE
SMTP service in (1) Microsoft Windows 2000 and (2) Internet Mail Connector (IMC) in Exchange Server 5.5 does not properly handle responses to NTLM authentication, which allows remote attackers to perform mail relaying via an SMTP AUTH command using null session credentials.
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Analysis
by VulDB Data Team • 09/23/2025
The vulnerability identified as CVE-2002-0054 represents a critical authentication flaw in Microsoft's messaging infrastructure that affects Windows 2000 systems and Exchange Server 5.5 with Internet Mail Connector. This issue stems from improper handling of NTLM authentication responses within the Simple Mail Transfer Protocol service, creating a pathway for unauthorized mail relaying operations. The flaw specifically manifests when the SMTP service processes AUTH commands with null session credentials, allowing malicious actors to exploit the authentication mechanism and gain unauthorized access to mail relay capabilities.
The technical root cause of this vulnerability lies in the insufficient validation of authentication responses within the NTLM authentication framework used by the SMTP service. When an attacker submits an SMTP AUTH command with null session credentials, the system fails to properly verify the authentication state, resulting in the service accepting the connection without proper authentication. This misconfiguration creates a condition where the mail server will relay messages without proper authorization, effectively turning the compromised system into an open relay. The vulnerability operates at the protocol level, exploiting weaknesses in how the SMTP service manages authentication handshakes and session validation.
The operational impact of this vulnerability is severe and multifaceted, as it enables attackers to exploit the compromised mail server for various malicious activities including spam distribution, phishing campaigns, and data exfiltration. Once an attacker successfully exploits this vulnerability, they can relay emails through the compromised server without restriction, potentially using it to send large volumes of spam messages that may be delivered to unsuspecting recipients. The vulnerability also provides a means for attackers to bypass normal mail server restrictions and access internal mail systems, potentially leading to further compromise of the network infrastructure. This type of vulnerability directly violates the principle of least privilege and undermines the security posture of organizations relying on affected Microsoft messaging platforms.
Organizations affected by this vulnerability should implement immediate mitigations including applying the relevant Microsoft security patches, configuring proper authentication requirements for SMTP services, and implementing network-level restrictions to prevent unauthorized access to mail relay capabilities. The vulnerability aligns with CWE-287, which addresses improper authentication issues, and maps to ATT&CK technique T1190 for exploitation of remote services and T1078 for valid accounts usage. Additional protective measures include implementing SMTP authentication requirements, configuring proper access controls, and monitoring mail server logs for unauthorized relay attempts. Network segmentation and firewall rules should be implemented to restrict access to SMTP services from untrusted networks, while regular security audits should verify that authentication mechanisms are properly configured and functioning as intended. The remediation process should also include comprehensive testing to ensure that legitimate mail relay operations continue to function properly while eliminating the security vulnerability that allows unauthorized access.