CVE-2007-0811 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 6.0 SP1 on Windows 2000, and 6.0 SP2 on Windows XP, allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) via an HTML document containing a certain JavaScript for loop with an empty loop body, possibly involving getElementById.
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Analysis
by VulDB Data Team • 08/22/2024
The vulnerability identified as CVE-2007-0811 represents a critical denial of service flaw affecting Microsoft Internet Explorer 6.0 versions running on Windows 2000 and Windows XP systems. This vulnerability stems from improper handling of specific JavaScript constructs within HTML documents, creating a condition where the browser engine encounters a NULL pointer dereference during normal operation. The flaw specifically manifests when processing JavaScript code containing a for loop with an empty loop body, combined with getElementById operations that trigger the problematic code path. The issue demonstrates a classic software reliability problem where the application fails to properly validate input parameters before attempting memory operations.
The technical implementation of this vulnerability exploits the JavaScript engine's handling of control flow structures, particularly focusing on the interaction between for loop constructs and DOM element retrieval methods. When Internet Explorer encounters an HTML document containing a JavaScript for loop with an empty body and calls getElementById, the browser's rendering engine attempts to process these operations in a manner that leads to NULL pointer dereference. This occurs because the JavaScript engine does not adequately validate the state of pointers or references before attempting to dereference them, resulting in an application crash that terminates the browser process. The vulnerability operates at the application layer and requires no special privileges or authentication to exploit, making it particularly dangerous in targeted attack scenarios.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged by attackers to create persistent denial of service conditions against targeted systems. When exploited successfully, the vulnerability causes Internet Explorer to crash immediately upon processing the malicious HTML content, forcing users to restart their browsers and potentially lose unsaved work. This type of attack can be particularly effective in social engineering campaigns where attackers craft malicious web pages designed to trigger the vulnerability when users visit compromised websites. The vulnerability affects systems running Windows 2000 and Windows XP with Internet Explorer 6.0 SP1 and SP2, representing a significant portion of enterprise environments that were still using these older operating systems and browsers at the time of discovery.
Mitigation strategies for this vulnerability primarily focus on immediate remediation through software updates and system hardening measures. Microsoft released security patches addressing this issue through their regular update cycle, emphasizing the importance of maintaining current system patches to protect against known vulnerabilities. Organizations should implement browser hardening techniques including disabling unnecessary JavaScript features, implementing content filtering solutions, and restricting access to potentially malicious websites. The vulnerability aligns with CWE-476 which identifies NULL pointer dereference as a common software flaw that leads to application instability and potential denial of service conditions. From an attack framework perspective, this vulnerability would be categorized under the denial of service tactic in the MITRE ATT&CK framework, specifically targeting the application layer to disrupt normal user operations and potentially create opportunities for further exploitation.
The broader implications of this vulnerability highlight the critical importance of proper input validation and error handling in browser engines, as well as the necessity of maintaining up-to-date security patches across enterprise environments. Organizations should implement comprehensive vulnerability management programs that include regular security assessments, automated patch deployment, and user education regarding safe browsing practices. The vulnerability also demonstrates the risks associated with legacy system support, as older versions of operating systems and browsers often contain unpatched security flaws that attackers can exploit to gain unauthorized access or disrupt services. Proper system monitoring and incident response procedures should include detection mechanisms for unusual browser crash patterns that might indicate exploitation of similar vulnerabilities.