CVE-2004-0840 in Windows
Summary
by MITRE
The SMTP (Simple Mail Transfer Protocol) component of Microsoft Windows XP 64-bit Edition, Windows Server 2003, Windows Server 2003 64-bit Edition, and the Exchange Routing Engine component of Exchange Server 2003, allows remote attackers to execute arbitrary code via a malicious DNS response message containing length values that are not properly validated.
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Analysis
by VulDB Data Team • 07/07/2025
The vulnerability described in CVE-2004-0840 represents a critical buffer overflow condition within the Simple Mail Transfer Protocol implementation of several Microsoft operating systems and server products. This flaw specifically affects the SMTP component running on Windows XP 64-bit Edition, Windows Server 2003, and Windows Server 2003 64-bit Edition, as well as the Exchange Routing Engine component of Exchange Server 2003. The vulnerability stems from inadequate validation of DNS response message length values during the mail routing process, creating a pathway for remote code execution attacks.
The technical exploitation of this vulnerability occurs when the affected SMTP services process DNS responses containing malformed length fields. When these services encounter DNS messages with improperly validated length values, they fail to properly bounds-check the data before processing it, leading to memory corruption that can be leveraged by attackers to execute arbitrary code on the target system. This type of flaw falls under the Common Weakness Enumeration category of CWE-121, which describes stack-based buffer overflow conditions, and more specifically relates to CWE-787, representing out-of-bounds write conditions that can result in arbitrary code execution. The vulnerability's impact is particularly severe because it allows remote attackers to gain system-level privileges without requiring authentication, making it a prime target for automated exploitation.
The operational impact of CVE-2004-0840 extends beyond simple remote code execution to encompass complete system compromise and potential network infiltration. Attackers can exploit this vulnerability to install backdoors, modify system files, establish persistent access, and potentially use the compromised system as a launch point for attacking other networked devices. The affected products include widely deployed enterprise mail servers and desktop operating systems, amplifying the potential attack surface. According to ATT&CK framework, this vulnerability maps to T1059.007 for command and script interpreter and T1068 for exploit for privilege escalation, as the initial compromise often leads to elevated system privileges. Organizations running these vulnerable systems face significant risk of data breaches, service disruption, and potential compliance violations, particularly in regulated environments where email security is paramount.
Mitigation strategies for this vulnerability require immediate patch management implementation across all affected systems, with Microsoft releasing security updates to address the DNS length validation flaws in the affected SMTP implementations. Network segmentation and firewall rules should be implemented to restrict unnecessary SMTP traffic and DNS queries from untrusted sources. Additionally, organizations should deploy intrusion detection systems that can identify suspicious DNS response patterns and monitor for exploitation attempts. The vulnerability demonstrates the importance of proper input validation and bounds checking in network services, particularly those handling external data such as DNS responses, and serves as a reminder of the critical need for regular security updates and vulnerability assessments in enterprise environments.