CVE-2002-0419 in IIS
Summary
by MITRE
Information leaks in IIS 4 through 5.1 allow remote attackers to obtain potentially sensitive information or more easily conduct brute force attacks via responses from the server in which (2) in certain configurations, the server IP address is provided as the realm for Basic authentication, which could reveal real IP addresses that were obscured by NAT, or (3) when NTLM authentication is used, the NetBIOS name of the server and its Windows NT domain are revealed in response to an Authorization request. NOTE: this entry originally contained a vector (1) in which the server reveals whether it supports Basic or NTLM authentication through 401 Access Denied error messages. CVE has REJECTED this vector; it is not a vulnerability because the information is already available through legitimate use, since authentication cannot proceed without specifying a scheme that is supported by both the client and the server.
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Analysis
by VulDB Data Team • 09/17/2025
The vulnerability described in CVE-2002-0419 represents a significant information disclosure issue affecting Microsoft Internet Information Services versions 4.0 through 5.1. This flaw exposes sensitive system information through server responses that occur during authentication processes, creating potential attack vectors for remote adversaries seeking to gather intelligence about target systems. The vulnerability operates within the context of web server security where authentication mechanisms inadvertently leak identifying information that could otherwise remain hidden through proper network configuration. The issue stems from how IIS handles authentication responses, specifically when dealing with Basic and NTLM authentication schemes, where server metadata becomes exposed in ways that compromise operational security and network architecture integrity.
The technical implementation of this vulnerability manifests through two primary vectors that exploit the server's response handling during authentication negotiations. The first vector involves Basic authentication where the server provides its actual IP address as the realm value in authentication challenges, effectively revealing the true server address that would normally be obscured by Network Address Translation mechanisms. This occurs because the authentication realm field contains the server's real IP address instead of a generic or obfuscated value, allowing attackers to discover the underlying network topology. The second vector involves NTLM authentication where responses to Authorization requests contain the NetBIOS name of the server and its associated Windows NT domain information. These disclosures occur during the normal authentication handshake process when the server responds to client authentication attempts, making the information leak unavoidable during legitimate authentication operations.
From an operational impact perspective, this vulnerability creates substantial risk for organizations relying on IIS 4.0 through 5.1 servers for their web services. The exposure of server IP addresses through Basic authentication can enable attackers to map network topologies and identify internal infrastructure that should remain hidden behind NAT devices. This information can facilitate more sophisticated attacks including targeted reconnaissance, network mapping, and social engineering operations. The disclosure of NetBIOS names and domain information through NTLM authentication provides additional intelligence about the Windows environment, potentially revealing organizational structure, domain naming conventions, and system configurations that could be leveraged in subsequent attacks. The vulnerability essentially undermines the security benefits of network segmentation and authentication scheme confidentiality, creating opportunities for attackers to conduct more effective brute force attacks by knowing the specific authentication mechanisms and system identifiers involved.
The security implications extend beyond simple information disclosure to encompass potential privilege escalation and attack chain acceleration. When attackers can determine the real IP addresses of servers behind NAT, they can more effectively target specific systems and potentially bypass certain network security controls. The revelation of domain information through NTLM responses can enable credential harvesting attacks and facilitate pass-the-hash or similar authentication bypass techniques. This vulnerability aligns with CWE-200 (Information Exposure) and represents a classic example of how authentication mechanisms can inadvertently expose system information. The ATT&CK framework categorizes this under T1087 (Account Discovery) and T1592 (Gather Victim Host Information) as it provides attackers with systematic ways to collect identifying information about target systems and their network configurations. Organizations with IIS 4.0 through 5.1 systems are particularly vulnerable as these legacy servers lack modern security hardening features and are often deployed in environments where network security assumptions have been violated through the use of NAT and other network translation mechanisms.
The mitigation strategies for this vulnerability focus on both immediate configuration changes and long-term architectural considerations. Organizations should disable or restrict the use of Basic authentication where possible, as this provides the most direct path for IP address disclosure. Configuration changes to ensure that authentication realms do not contain actual server IP addresses can help address the first vector. For NTLM authentication, organizations should consider implementing additional network security controls such as network segmentation and access control lists to limit exposure of authentication endpoints. The recommended approach includes upgrading to newer versions of IIS that have addressed these information disclosure issues, implementing proper network design principles that minimize reliance on NAT for security, and establishing monitoring procedures to detect unauthorized authentication attempts that might exploit these vulnerabilities. Security teams should also consider implementing authentication logging and monitoring to detect unusual patterns that might indicate exploitation attempts targeting these specific information disclosure vectors.