CVE-2006-1992 in Internet Explorer
Summary
by MITRE
mshtml.dll 6.00.2900.2873, as used in Microsoft Internet Explorer, allows remote attackers to cause a denial of service (crash) via nested OBJECT tags, which trigger invalid pointer dereferences including NULL dereferences. NOTE: the possibility of code execution was originally theorized, but Microsoft has stated that this issue is non-exploitable.
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Analysis
by VulDB Data Team • 03/12/2021
The vulnerability identified as CVE-2006-1992 affects Microsoft Internet Explorer through its mshtml.dll component version 6.00.2900.2873, representing a critical denial of service weakness that manifests through improper handling of nested OBJECT tags within web content. This flaw resides within the browser's HTML parsing and rendering engine, specifically demonstrating how malformed nested object elements can trigger system instability. The vulnerability operates by exploiting memory management issues within the mshtml.dll library, where the processing of deeply nested OBJECT elements causes the application to attempt accessing invalid memory addresses, resulting in immediate application termination. The technical implementation involves the browser's failure to properly validate the structure of nested HTML elements, particularly when OBJECT tags contain other OBJECT tags, creating a scenario where pointer arithmetic leads to NULL dereference conditions.
The operational impact of this vulnerability extends beyond simple service disruption, as it represents a fundamental flaw in how Internet Explorer handles complex HTML structures that could potentially be leveraged in broader attack scenarios. When exploited, the vulnerability causes Internet Explorer to crash and terminate unexpectedly, effectively denying users access to web content and disrupting normal browsing operations. Security researchers initially theorized this issue might enable code execution due to the nature of pointer dereference vulnerabilities, which often present potential for privilege escalation or arbitrary code execution pathways. However, Microsoft's official assessment has clarified that this specific vulnerability does not permit remote code execution, categorizing it as a pure denial of service condition. The vulnerability aligns with CWE-476, which describes NULL pointer dereference conditions that can lead to application crashes and system instability. This classification indicates the flaw stems from inadequate null pointer validation during HTML element processing, where the application fails to properly check if object references are valid before attempting to access them.
The exploitation of CVE-2006-1992 demonstrates how seemingly benign HTML elements can be weaponized to create system instability, particularly in older browser versions where memory management was less robust. Attackers could craft malicious web pages containing nested OBJECT tags that, when loaded in Internet Explorer, would trigger the memory access violations and subsequent browser crashes. This vulnerability particularly affects systems running Windows XP with Internet Explorer 6.0, as this represents the primary affected configuration where the mshtml.dll version 6.00.2900.2873 resides. The flaw's potential for causing widespread disruption lies in its ability to crash browsers through standard web browsing activities, making it particularly dangerous in environments where users frequently access untrusted web content. Organizations with older Windows systems running Internet Explorer 6.0 should consider immediate remediation through security updates or browser upgrades, as this vulnerability represents a significant risk to system availability. The ATT&CK framework categorizes this type of vulnerability under privilege escalation and denial of service tactics, though the current assessment indicates it does not provide code execution capabilities. Mitigation strategies should focus on updating to newer Internet Explorer versions or implementing browser security restrictions that prevent loading of potentially malicious nested HTML elements, particularly in enterprise environments where legacy systems remain in use.