CVE-2004-1312 in Mailessentials
Summary
by MITRE
A bug in the HTML parser in a certain Microsoft HTML library, as used in various third party products, may allow remote attackers to cause a denial of service via certain strings, as reported in GFI MailEssentials for Exchange 9 and 10, and GFI MailSecurity for Exchange 8, which causes emails to remain in IIS or Exchange mail queues.
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Analysis
by VulDB Data Team • 06/30/2018
The vulnerability identified as CVE-2004-1312 represents a critical flaw in the HTML parsing functionality of a Microsoft HTML library that has been incorporated into numerous third-party email security solutions. This issue stems from inadequate input validation within the HTML parser component, which fails to properly handle malformed or specially crafted HTML content. The vulnerability affects widely deployed email security products including GFI MailEssentials for Exchange versions 9 and 10, as well as GFI MailSecurity for Exchange version 8, making it a significant concern for enterprise email environments that rely on these protection mechanisms.
The technical nature of this vulnerability manifests when the affected HTML parser encounters specific malformed strings within email content that trigger an unexpected behavior in the parsing process. These malformed strings are carefully constructed to exploit the parser's lack of proper boundary checking and error handling mechanisms. When the parser processes such inputs, it enters a state where it cannot properly terminate the parsing operation, leading to resource exhaustion and subsequent system instability. This particular flaw operates at the application layer and leverages the inherent weaknesses in how the HTML library handles malformed content, creating a condition where the parser becomes trapped in an infinite loop or consumes excessive memory resources.
The operational impact of this vulnerability extends beyond simple service disruption, creating a persistent denial of service condition that affects email infrastructure at the messaging queue level. When malicious emails containing the specially crafted HTML strings are processed by the affected systems, they cause emails to remain indefinitely in the IIS or Exchange mail queues, effectively blocking legitimate email traffic and creating a backlog that can severely impact business communications. This behavior creates a cascading effect where the mail queues fill up, preventing new emails from being processed and potentially causing the entire email system to become unresponsive. The vulnerability essentially creates a resource starvation condition that affects the core functionality of the email infrastructure, making it impossible for users to send or receive emails until the affected queues are manually cleared.
Organizations affected by this vulnerability should implement immediate mitigations including applying the vendor patches released for the affected GFI products, implementing email content filtering rules that block HTML content from suspicious sources, and configuring rate limiting mechanisms to prevent excessive processing of malformed emails. The vulnerability aligns with CWE-129, which describes improper validation of input boundaries, and demonstrates characteristics consistent with ATT&CK technique T1499.004 for network denial of service attacks. Security administrators should also consider implementing email header analysis to identify potentially malicious content before it reaches the HTML parsing stage, and establish monitoring procedures to detect unusual queue behavior that may indicate exploitation of this vulnerability. Additionally, organizations should conduct thorough testing of any applied patches in isolated environments before deployment to ensure that the fixes do not introduce compatibility issues with existing email infrastructure.