CVE-2005-4717 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 6.0 on Windows NT 4.0 SP6a, Windows 2000 SP4, Windows XP SP1, Windows XP SP2, and Windows Server 2003 SP1 allows remote attackers to cause a denial of service (client crash) via a certain combination of a malformed HTML file and a CSS file that triggers a null dereference, probably related to rendering of a DIV element that contains a malformed IMG tag, as demonstrated by IEcrash.htm and IEcrash.rar.
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Analysis
by VulDB Data Team • 05/07/2019
This vulnerability represents a critical denial of service flaw in Microsoft Internet Explorer 6.0 across multiple Windows operating systems including Windows NT 4.0 SP6a, Windows 2000 SP4, Windows XP SP1 and SP2, and Windows Server 2003 SP1. The issue stems from improper handling of malformed HTML and CSS combinations during the browser's rendering process, specifically when processing DIV elements containing malformed IMG tags. The vulnerability manifests as a null dereference condition that causes the browser client to crash and terminate unexpectedly, effectively rendering the affected system unusable for web browsing operations.
The technical exploitation involves crafting a specific combination of HTML and CSS files that triggers an internal memory access violation within Internet Explorer's rendering engine. When the browser attempts to process a DIV element that contains a malformed IMG tag, the parsing logic fails to properly validate the structure, leading to a null pointer dereference during the rendering phase. This type of vulnerability falls under CWE-476 which specifically addresses NULL Pointer Dereference conditions in software implementations. The attack vector requires remote delivery of malicious content through web-based vectors, making it particularly dangerous as users can be compromised simply by visiting malicious websites or opening compromised email attachments containing the malicious HTML files.
The operational impact of this vulnerability extends beyond simple service disruption as it represents a potential entry point for more sophisticated attacks. While the immediate effect is a client crash, the underlying memory corruption could potentially be exploited for privilege escalation or code execution if attackers can control the memory layout and execution flow. The vulnerability affects a wide range of legacy systems that were still in production use during the time of discovery, making it particularly concerning for enterprise environments with older infrastructure. From an adversarial perspective, this flaw aligns with ATT&CK technique T1203 which involves exploiting software vulnerabilities to gain system access, though the initial impact is limited to denial of service rather than direct exploitation.
Mitigation strategies for this vulnerability include immediate patch deployment through Microsoft's security update channels, which would address the underlying rendering engine flaw. Organizations should also implement web content filtering and sandboxing measures to prevent automatic execution of potentially malicious HTML content. Browser isolation techniques and network segmentation can help limit the impact if exploitation occurs. Additionally, user education regarding suspicious web content and email attachments remains crucial, as the vulnerability can be triggered through social engineering attacks. System administrators should ensure that all affected systems receive the appropriate security patches and that legacy systems are properly decommissioned or upgraded to supported browser versions. The vulnerability underscores the importance of regular security updates and proper vulnerability management practices in maintaining secure computing environments.