CVE-2004-0484 in Internet Explorer
Summary
by MITRE
mshtml.dll in Microsoft Internet Explorer 6.0.2800 allows remote attackers to cause a denial of service (crash) via a table containing a form that crosses multiple td elements, and whose "float: left" class is defined in a link to a CSS stylesheet after the end of the table, which may trigger a null dereference.
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Analysis
by VulDB Data Team • 07/28/2025
The vulnerability described in CVE-2004-0484 represents a critical memory corruption issue within Microsoft Internet Explorer 6.0.2800's mshtml.dll component that enables remote attackers to execute denial of service attacks through carefully crafted HTML content. This flaw specifically manifests when Internet Explorer processes table structures containing forms that span across multiple td elements while simultaneously utilizing CSS styling with float:left properties. The vulnerability stems from improper memory management within the browser's HTML rendering engine, creating conditions where the application attempts to dereference null pointers during the rendering process. The attack vector requires an attacker to construct HTML content where a table structure contains a form element that extends across multiple table data cells, followed by CSS styling that defines a float:left property on a class that is referenced in a link to an external stylesheet. The timing of this CSS definition relative to the table structure's end creates a scenario where the browser's rendering engine encounters a null pointer reference, leading to application instability and subsequent crashes.
This vulnerability directly maps to CWE-476, which describes NULL Pointer Dereference, a common class of memory safety issues where software attempts to access memory at a null pointer location. The issue also aligns with ATT&CK technique T1203, which covers "Exploitation for Client Execution" as attackers can leverage this flaw to cause unintended application behavior through malicious web content. The technical implementation involves the browser's HTML parser and rendering engine failing to properly handle the interaction between table element boundaries, form element containment, and CSS property application. When Internet Explorer encounters the specific combination of table structure spanning multiple cells, embedded form elements, and CSS float properties defined in external stylesheets, the mshtml.dll component fails to maintain proper memory references, resulting in the null pointer dereference that terminates the application process. The vulnerability's exploitation requires precise control over HTML document structure and CSS loading order, making it particularly challenging to trigger through casual browsing but feasible in targeted attacks.
The operational impact of this vulnerability extends beyond simple application crashes, as it can be leveraged by attackers to disrupt user productivity and potentially serve as a precursor to more sophisticated attacks. When exploited, the vulnerability causes Internet Explorer to terminate unexpectedly, forcing users to restart their browsers and potentially lose unsaved work or session data. This denial of service capability can be particularly problematic in enterprise environments where multiple users rely on consistent browser functionality for business operations. The vulnerability affects Microsoft Internet Explorer 6.0.2800 specifically, though similar issues may exist in other versions of the mshtml.dll component that share the same underlying memory management flaws. Organizations using older versions of Internet Explorer face increased risk as these browsers lack modern security mitigations and are no longer supported with security updates. The vulnerability's impact is amplified when considering that Internet Explorer 6 was widely deployed in enterprise environments, making it a prime target for attackers seeking to disrupt business operations through simple web-based attacks.
Mitigation strategies for CVE-2004-0484 should focus on immediate remediation through Microsoft's security updates and patches, as well as network-level protections to prevent exploitation of the vulnerability. Microsoft released patches addressing this specific memory corruption issue, and organizations should prioritize applying these updates to all affected systems. Network administrators can implement content filtering solutions to block access to known malicious web sites that may contain exploit code targeting this vulnerability. Browser hardening techniques, including disabling automatic loading of external CSS files and implementing strict content security policies, can reduce the attack surface for this particular flaw. Additionally, organizations should consider implementing browser isolation techniques and using more modern browsers that have better memory management and security features. Security monitoring should include detection of unusual browser crash patterns and unexpected termination of Internet Explorer processes, as these may indicate exploitation attempts. The vulnerability also highlights the importance of proper HTML and CSS validation in web content, as the issue stems from malformed document structures that can be prevented through better development practices and content validation processes.