CVE-2006-3545 in Internet Explorer
Summary
by MITRE
** DISPUTED ** Microsoft Internet Explorer 7.0 Beta allows remote attackers to cause a denial of service (application crash) via a web page with multiple empty APPLET start tags. NOTE: a third party has disputed this issue, stating that the crash does not occur with Microsoft Internet Explorer 7.0 Beta3.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 06/19/2025
This vulnerability involves a denial of service condition in Microsoft Internet Explorer 7.0 Beta that could be exploited by remote attackers through specially crafted web pages containing multiple empty APPLET start tags. The issue manifests as an application crash that effectively renders the browser unavailable to users. The vulnerability was initially reported as affecting the beta version of Internet Explorer 7.0, which was under development and testing phases. The specific technical mechanism involves the browser's handling of malformed HTML elements, particularly the APPLET tag which is used to embed Java applets within web pages. When multiple empty APPLET start tags are present in a web page, the browser's rendering engine appears to encounter a parsing error that leads to a crash condition.
The technical flaw stems from insufficient input validation and error handling within the HTML parser component of Internet Explorer 7.0 Beta. When processing these malformed APPLET tags, the browser fails to properly manage the parsing state, resulting in a memory corruption or stack overflow condition that terminates the application process. This type of vulnerability falls under the category of improper input validation as defined by CWE-20, where the application does not adequately validate or sanitize input data before processing it. The vulnerability represents a classic case of resource exhaustion or memory management failure that occurs during HTML parsing operations.
From an operational impact perspective, this vulnerability could be exploited in a man-in-the-middle attack scenario where an attacker controls a web page that users might visit, or through malicious advertisements that contain the problematic HTML code. The denial of service effect would prevent users from accessing the browser entirely until it is manually restarted, potentially disrupting business operations or personal productivity. The vulnerability also represents a potential vector for more sophisticated attacks if the crash condition can be leveraged to execute arbitrary code, though the initial report only indicates a denial of service. This type of vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks and represents a fundamental security weakness in browser implementation.
The disputed nature of this vulnerability, as noted in the description, indicates that the issue may not manifest consistently across different versions of the software. The third-party dispute specifically mentions that the crash does not occur with Microsoft Internet Explorer 7.0 Beta3, suggesting that the vulnerability may have been addressed in subsequent builds or that the original report was based on an incorrect interpretation of the behavior. This highlights the importance of version-specific vulnerability assessment and the potential for false positives in vulnerability reporting. Organizations should verify the actual existence of the vulnerability in their specific software versions before implementing any remediation measures.
The broader implications of this vulnerability demonstrate the challenges inherent in browser security, where complex HTML parsing engines can contain numerous edge cases that lead to instability. The APPLET tag handling represents a legacy feature that was becoming obsolete as web technologies evolved, yet its improper handling in the browser engine created a security risk. This vulnerability underscores the need for comprehensive testing of edge cases in web browsers and the importance of maintaining robust error handling mechanisms. Security professionals should consider this vulnerability as an example of how seemingly minor parsing issues can result in significant operational disruptions and potential security implications. The vulnerability also illustrates the importance of timely patching and version management in enterprise environments where older software versions may contain unpatched security flaws.