CVE-2004-1616 in Links
Summary
by MITRE
Links allows remote attackers to cause a denial of service (memory consumption) via a web page or HTML email that contains a table with a td element and a large rowspan value,as demonstrated by mangleme.
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Analysis
by VulDB Data Team • 06/21/2018
The vulnerability identified as CVE-2004-1616 represents a classic denial of service flaw affecting web browsers and email clients that process html content. This issue specifically targets the rendering engine's handling of table elements, particularly the td (table data) element combined with excessive rowspan attributes. The flaw demonstrates how seemingly benign html markup can be exploited to consume excessive system resources, ultimately leading to service unavailability. The vulnerability was demonstrated through the mangleme exploit which crafted malicious html content designed to trigger memory exhaustion in affected applications. This type of attack falls under the category of resource exhaustion attacks where attackers leverage legitimate application features to consume system resources beyond normal operational limits.
The technical root cause of this vulnerability lies in the insufficient input validation and resource management within html rendering engines. When a browser encounters a table element with a td tag containing an extremely large rowspan value, the rendering engine attempts to allocate memory to accommodate the specified number of rows. This allocation process lacks proper bounds checking and resource limiting mechanisms, allowing attackers to specify values that cause the application to consume excessive memory resources. The flaw is particularly dangerous because it can be triggered through multiple vectors including web pages and html email content, making it accessible to attackers through various communication channels. This vulnerability directly relates to CWE-770, which addresses allocation of resources without limits or with inadequate limits, and demonstrates how improper resource management can lead to denial of service conditions.
The operational impact of CVE-2004-1616 extends beyond simple service disruption to potentially affect system stability and availability across multiple platforms. When exploited, the vulnerability can cause applications to consume all available memory resources, leading to system crashes, application hangs, or complete system unresponsiveness. The attack vector through html email makes this particularly concerning for enterprise environments where email systems are critical infrastructure components. Security professionals should note that this vulnerability demonstrates the importance of input sanitization and resource limiting in web applications, as well as the need for proper html parsing and rendering engine security. The flaw also aligns with ATT&CK technique T1499.004 which covers resource exhaustion attacks targeting memory and storage resources.
Mitigation strategies for this vulnerability require a multi-layered approach focusing on both application-level defenses and network-level protections. Organizations should implement html content filtering and sanitization mechanisms that limit table element attributes to reasonable values, particularly rowspan and colspan attributes. Browser vendors and email client developers should enhance their rendering engines with proper bounds checking and resource allocation limits for table elements. Network-level protections including content filtering appliances and email security gateways can help prevent malicious html content from reaching end users. Additionally, regular security updates and patches should be applied to ensure that rendering engines have proper input validation and resource management controls. System administrators should monitor for unusual memory consumption patterns that might indicate exploitation attempts, and implement proper resource limits on web and email applications to prevent complete system exhaustion. The vulnerability underscores the importance of defensive programming practices and the need for comprehensive security testing of html parsing and rendering functionality.