CVE-2006-3591 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 6 allows remote attackers to cause a denial of service (application crash) by accessing the URL property of a TriEditDocument.TriEditDocument object before it has been initialized, which triggers a NULL pointer dereference.
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Analysis
by VulDB Data Team • 07/12/2021
Microsoft Internet Explorer 6 contains a critical vulnerability that manifests as a null pointer dereference when handling TriEditDocument objects, specifically when accessing the URL property before object initialization. This flaw resides in the browser's handling of ActiveX controls and represents a classic buffer overflow condition that can be exploited to cause application instability. The vulnerability is classified under CWE-476 as NULL pointer dereference, which occurs when software attempts to access a memory location through a pointer that has not been properly initialized to point to valid memory. The attack vector requires remote execution since an attacker can craft malicious web content that triggers this condition when a user visits a compromised website, making it particularly dangerous in web-based attack scenarios.
The technical implementation of this vulnerability occurs within the TriEditDocument object model where the URL property access triggers a memory access violation when the object has not been fully constructed or initialized. When Internet Explorer attempts to read the URL property of an uninitialized TriEditDocument.TriEditDocument object, the software follows a null pointer reference that results in an immediate application crash. This behavior aligns with the ATT&CK technique T1203, which involves gaining access to systems through application vulnerabilities, specifically targeting browser rendering engines and object handling mechanisms. The flaw exists because the browser's object model does not properly validate whether the TriEditDocument object has been initialized before allowing property access operations.
The operational impact of this vulnerability extends beyond simple application crashes, as it provides attackers with a reliable method for disrupting user sessions and potentially creating conditions for more sophisticated attacks. When a user encounters a malicious webpage containing the exploit, the browser will terminate unexpectedly, forcing users to restart their browsing session and potentially lose unsaved work. This denial of service condition can be amplified through various social engineering techniques, where attackers craft convincing phishing pages or compromise legitimate websites to deliver the malicious content. The vulnerability affects all versions of Internet Explorer 6 that support the TriEditDocument ActiveX control, making it particularly concerning given the widespread deployment of this browser version during the affected period.
Mitigation strategies for this vulnerability include immediate deployment of Microsoft security patches that address the uninitialized object access issue, along with browser configuration changes that restrict ActiveX control execution. Organizations should implement security policies that disable or restrict TriEditDocument ActiveX controls in Internet Explorer environments, particularly in high-risk scenarios where users may encounter untrusted content. Network-level protections such as web application firewalls and content filtering solutions can help detect and block malicious URLs that attempt to exploit this vulnerability. Additionally, users should be educated about the risks of visiting untrusted websites and the importance of keeping their browser software updated to prevent exploitation. The vulnerability demonstrates the importance of proper object initialization validation in software development practices and aligns with security standards that emphasize input validation and defensive programming techniques to prevent memory access violations.