CVE-2006-7030 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 6 SP2 and earlier allows remote attackers to cause a denial of service (crash) via certain malformed HTML, possibly involving applet and base tags without required arguments, which triggers a null pointer dereference in mshtml.dll.
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Analysis
by VulDB Data Team • 07/13/2021
Microsoft Internet Explorer 6 Service Pack 2 and earlier versions contain a critical denial of service vulnerability that stems from improper handling of malformed HTML content. This vulnerability specifically affects the mshtml.dll component which serves as the core rendering engine for web content in Internet Explorer. The flaw manifests when the browser encounters HTML constructs that lack required arguments for applet and base tags, creating a scenario where the application attempts to dereference a null pointer during the parsing process. This null pointer dereference represents a classic software bug pattern that can lead to application instability and complete crash conditions.
The technical implementation of this vulnerability involves the browser's HTML parser encountering malformed applet and base tags that do not contain their required attributes or parameters. When mshtml.dll attempts to process these malformed elements, it fails to properly validate the presence of essential arguments before attempting to access related memory structures. This validation failure results in a null pointer dereference error that terminates the browser process entirely. The vulnerability falls under the category of improper input validation as defined by CWE-20, specifically involving the lack of proper parameter checking for HTML elements. The attack vector is remote and requires no authentication, making it particularly dangerous as it can be exploited through web pages without user interaction beyond visiting a malicious site.
The operational impact of this vulnerability extends beyond simple browser crashes to potentially disrupt user productivity and create security risks in enterprise environments. When exploited, the vulnerability causes Internet Explorer to terminate abruptly, forcing users to restart their browsers and potentially lose unsaved work. In corporate settings where multiple users rely on consistent browser functionality, this can lead to significant operational disruption. The vulnerability is particularly concerning because it can be triggered through standard web browsing activities, making it difficult for users to protect themselves without technical intervention. The attack surface includes any web content that might contain malformed HTML, including legitimate websites that may have been compromised or malicious sites specifically designed to exploit this weakness.
Mitigation strategies for this vulnerability should focus on immediate remediation through software updates and patches provided by Microsoft. Users should upgrade to Internet Explorer 7 or later versions where this vulnerability has been addressed through improved HTML parsing and input validation mechanisms. Organizations should implement network-level protections such as web content filtering systems that can identify and block potentially malicious HTML content before it reaches user browsers. Security teams should also consider implementing browser hardening measures that restrict the execution of potentially dangerous HTML elements and ensure proper input validation occurs at multiple layers of the application stack. Additionally, regular security awareness training can help users recognize suspicious web content that might exploit this vulnerability, while system monitoring should be implemented to detect unusual browser crash patterns that could indicate exploitation attempts. This vulnerability aligns with ATT&CK technique T1211 which involves exploitation of software vulnerabilities for denial of service purposes, and demonstrates the importance of maintaining current security patches and implementing layered defense strategies to protect against such attacks.