CVE-2006-3511 in Internet Explorer
Summary
by MITRE
Internet Explorer 6 on Windows XP SP2 allows remote attackers to cause a denial of service (crash) by setting the fonts property of the HtmlDlgSafeHelper object, which triggers a null dereference.
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Analysis
by VulDB Data Team • 04/07/2017
The vulnerability identified as CVE-2006-3511 represents a critical denial of service flaw in Internet Explorer 6 running on Windows XP Service Pack 2 systems. This vulnerability specifically targets the HtmlDlgSafeHelper object within the browser's component model, exploiting a fundamental memory management issue that results in application instability and system crash. The flaw manifests when remote attackers manipulate the fonts property of this particular object, creating conditions that lead to a null pointer dereference within the browser's execution environment.
The technical root cause of this vulnerability lies in improper input validation and memory handling within Internet Explorer's implementation of the HtmlDlgSafeHelper object. When the fonts property is set to specific values, the browser fails to properly validate the input parameters before attempting to access memory locations. This null dereference condition occurs because the application attempts to access a memory address that has not been properly initialized or allocated, causing the browser process to terminate unexpectedly. The vulnerability falls under the category of memory corruption flaws and aligns with CWE-476 which specifically addresses null pointer dereference issues in software implementations. This type of vulnerability is particularly dangerous because it can be triggered remotely without requiring user interaction, making it an attractive target for automated exploitation campaigns.
The operational impact of this vulnerability extends beyond simple service disruption to potentially enable more sophisticated attack vectors. While the primary effect is a denial of service causing browser crashes, the underlying memory corruption vulnerability creates opportunities for attackers to escalate their privileges or execute arbitrary code. The vulnerability affects systems where Internet Explorer 6 operates on Windows XP SP2, which was a widely deployed platform at the time of discovery. This widespread adoption made the vulnerability particularly dangerous as it could impact a large number of systems simultaneously, potentially causing cascading failures in enterprise environments where browser stability is critical for business operations. The vulnerability's remote exploitability means that attackers can trigger the condition from outside the local network, making it a significant threat to organizations with exposed web services or systems that might be accessed by untrusted users.
Mitigation strategies for this vulnerability should focus on immediate patch deployment through Microsoft's security updates, as well as implementing network-level protections to prevent unauthorized access to systems running vulnerable versions of Internet Explorer. Organizations should consider implementing browser isolation techniques and restricting access to potentially malicious web content through proxy servers and content filtering solutions. The vulnerability demonstrates the importance of proper input validation and memory management in browser security, highlighting how seemingly minor implementation flaws can result in significant system instability. Security teams should also consider implementing monitoring solutions to detect unusual browser crash patterns that might indicate exploitation attempts. This vulnerability serves as a reminder of the critical need for comprehensive security testing and the importance of maintaining up-to-date software implementations to prevent exploitation of known memory corruption vulnerabilities. The attack pattern associated with this vulnerability aligns with ATT&CK technique T1203 which covers legitimate program execution through manipulation of program execution flow, emphasizing how such flaws can be leveraged to disrupt normal system operations and potentially enable further compromise.