CVE-2002-1790 in IIS
Summary
by MITRE
The SMTP service in Microsoft Internet Information Services (IIS) 4.0 and 5.0 allows remote attackers to bypass anti-relaying rules and send spam or spoofed messages via encapsulated SMTP addresses, a similar vulnerability to CVE-1999-0682.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 06/08/2025
The vulnerability described in CVE-2002-1790 represents a critical flaw in the Simple Mail Transfer Protocol implementation within Microsoft Internet Information Services versions 4.0 and 5.0. This weakness specifically affects the SMTP service component that handles email relay operations, creating a pathway for malicious actors to exploit the server's mail handling capabilities. The vulnerability operates at the protocol level, leveraging fundamental aspects of how SMTP addresses are processed and validated within the IIS environment. According to CWE-284, this issue stems from improper access control mechanisms that fail to properly validate sender addresses during the relay process. The flaw enables attackers to circumvent the built-in anti-relaying protections that are designed to prevent unauthorized systems from using the IIS server as an open relay for sending unsolicited emails.
The technical exploitation of this vulnerability occurs through the manipulation of SMTP address encapsulation techniques that allow attackers to craft specially formatted email addresses which bypass the normal validation checks. When the IIS SMTP service processes these malformed addresses, it fails to properly verify the authenticity of the sending domain or the legitimate relay permissions associated with the address. This creates a scenario where unauthorized users can send email messages through the compromised server without proper authentication or authorization. The vulnerability is particularly dangerous because it operates at the network protocol level rather than application level, making it difficult to detect through traditional application security measures. The attack vector involves sending emails with addresses that contain embedded or encoded information that tricks the SMTP service into accepting them as legitimate relay targets.
The operational impact of this vulnerability extends beyond simple spam distribution, as it enables sophisticated phishing campaigns, email spoofing attacks, and large-scale spam operations that can damage the reputation of the compromised server and its associated domain. Organizations running affected IIS versions become unwitting participants in email abuse networks, potentially leading to their servers being blacklisted by major email providers and security vendors. The vulnerability directly relates to ATT&CK technique T1192, which involves the use of compromised systems for sending spam or phishing emails, and represents a classic example of how protocol-level flaws can be leveraged for widespread abuse. Network administrators face significant challenges in monitoring and detecting such attacks because they appear to originate from legitimate server addresses, making attribution and forensic analysis difficult. The impact is particularly severe for businesses that rely heavily on email communications, as their systems become compromised and used for malicious activities without their knowledge or consent.
Mitigation strategies for this vulnerability require immediate implementation of security patches provided by Microsoft, as the flaw exists in the core SMTP service functionality of IIS 4.0 and 5.0. Organizations should also implement additional network-level protections such as proper firewall rules, SMTP relay restrictions, and monitoring of unusual email traffic patterns. The solution involves disabling unnecessary relay capabilities, implementing proper authentication mechanisms, and regularly reviewing SMTP service configurations to ensure that anti-relaying rules remain effective. Security professionals should consider implementing email authentication standards such as SPF, DKIM, and DMARC to help prevent abuse of compromised systems, while also establishing network monitoring procedures to detect anomalous email relay patterns. Organizations should also evaluate their overall email security posture and consider migrating to more modern email server solutions that have better security controls and more frequent security updates to prevent similar vulnerabilities from arising in the future.