CVE-2006-7065 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer allows remote attackers to cause a denial of service (crash) via an IFRAME with a certain XML file and XSL stylesheet that triggers a crash in mshtml.dll when a refresh is called, probably a null pointer dereference.
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Analysis
by VulDB Data Team • 07/13/2021
This vulnerability resides within Microsoft Internet Explorer's handling of XML and XSLT processing, specifically affecting the mshtml.dll component that serves as the core rendering engine for web content. The flaw manifests when a maliciously crafted IFRAME element references an XML file accompanied by a particular XSL stylesheet, creating a scenario where subsequent page refresh operations trigger an unexpected crash in the browser's rendering subsystem. The technical root cause appears to be a null pointer dereference condition within the mshtml.dll module, which occurs during the processing of the XML transformation operations. This type of vulnerability falls under the category of memory corruption issues that can be exploited to cause application instability and system crashes, representing a classic denial of service vector that can be leveraged by remote attackers without requiring authentication or user interaction beyond visiting a malicious webpage.
The operational impact of this vulnerability extends beyond simple browser instability, as it can be weaponized to disrupt user productivity and potentially serve as a precursor to more sophisticated attacks. When the null pointer dereference occurs during the refresh operation, the mshtml.dll module crashes, forcing Internet Explorer to terminate and potentially causing loss of unsaved work or session data. This vulnerability demonstrates a critical weakness in the XML processing pipeline of Internet Explorer, where the application fails to properly validate or handle malformed XSLT transformations before executing them during refresh cycles. The attack vector is particularly concerning because it requires no user interaction beyond viewing the malicious content, making it a passive threat that can be delivered through various means including email attachments, compromised websites, or malicious advertisements.
Security researchers have identified this vulnerability as a variant of memory corruption issues that align with CWE-476, which specifically addresses null pointer dereference conditions in software implementations. The vulnerability also maps to ATT&CK technique T1203, which covers the exploitation of software vulnerabilities to cause denial of service conditions. The presence of such flaws in widely deployed browser components like mshtml.dll creates a significant risk landscape where attackers can leverage these weaknesses to disrupt service availability for users across organizations. The fact that the crash occurs specifically during refresh operations indicates that the vulnerability may be exploitable in scenarios where users are actively browsing or where automated page refresh mechanisms are in place. Organizations should consider this vulnerability as part of their broader security posture assessment, particularly in environments where Internet Explorer remains in use despite Microsoft's end of support for the browser.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected systems, as Microsoft has released security updates to address the underlying memory corruption issue. Administrators should also implement network-level protections such as web application firewalls that can detect and block malicious XML content, particularly when it contains XSLT transformations that might trigger the vulnerable code path. Browser hardening techniques including disabling automatic refresh features, restricting IFRAME usage, and implementing content security policies can provide additional defense layers. Security monitoring should focus on detecting unusual patterns of browser crashes or mshtml.dll process terminations that might indicate exploitation attempts. Organizations should also consider implementing sandboxing techniques for Internet Explorer usage and transitioning to modern browser alternatives that have more robust memory safety mechanisms and active security updates. The vulnerability serves as a reminder of the importance of maintaining up-to-date security patches and the risks associated with legacy browser support in enterprise environments.