CVE-2002-0101 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 6.0 and earlier allows local users to cause a denial of service via an infinite loop for modeless dialogs showModelessDialog, which causes CPU usage while the focus for the dialog is not released.
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Analysis
by VulDB Data Team • 06/08/2017
The vulnerability identified as CVE-2002-0101 represents a significant denial of service flaw within Microsoft Internet Explorer versions 6.0 and earlier, specifically affecting the handling of modeless dialogs through the showModelessDialog method. This issue stems from a fundamental design flaw in how the browser processes certain dialog operations, creating a condition where the system becomes trapped in an infinite loop while maintaining focus on the problematic dialog interface. The flaw manifests when local users exploit the showModelessDialog API function, which is designed to display non-modal dialog boxes that remain active even when the user interacts with other parts of the application or system.
The technical implementation of this vulnerability involves the improper handling of dialog state management within Internet Explorer's rendering engine. When the showModelessDialog method is invoked with specific parameters that trigger the problematic code path, the browser enters a continuous loop where it repeatedly attempts to process the dialog state without properly releasing the focus or terminating the operation. This results in sustained high CPU utilization as the system continuously processes the same dialog operations, effectively consuming system resources and rendering the browser unresponsive to user input while the malicious code executes. The infinite loop prevents the dialog from properly closing or releasing system resources, creating a persistent denial of service condition that can severely impact system performance and user experience.
From an operational perspective, this vulnerability presents a substantial risk to users running older versions of Internet Explorer, particularly in environments where system resources are constrained or where multiple applications are running concurrently. The denial of service condition can be triggered by simply visiting a malicious web page that contains JavaScript code utilizing the vulnerable showModelessDialog method, making it a particularly dangerous flaw for widespread exploitation. The continuous CPU usage can lead to system instability, application crashes, and in severe cases, complete system freezes or hangs, especially when the affected browser instance is running critical system processes or when multiple instances are affected simultaneously. This vulnerability directly impacts the availability and usability of the affected system, potentially preventing users from accessing legitimate web content or performing essential computing tasks.
The vulnerability aligns with CWE-835, which specifically addresses the issue of infinite loops in software implementations, and demonstrates how improper resource management can lead to denial of service conditions. From an ATT&CK framework perspective, this vulnerability falls under the T1499.004 technique related to network denial of service, as it effectively consumes system resources to prevent normal operation. Additionally, it represents a classic example of a local privilege escalation vector through resource exhaustion, as local users can exploit this condition without requiring elevated privileges or network access. The flaw also relates to T1566.001, which covers social engineering techniques involving malicious web content, as users can be tricked into visiting compromised websites that trigger the vulnerable code path. Organizations should implement immediate mitigations including browser updates to newer versions, disabling the showModelessDialog functionality through security policies, or implementing network-based protections that can detect and block malicious JavaScript patterns associated with this vulnerability, while also ensuring comprehensive patch management across all affected systems to prevent exploitation.