CVE-2006-5805 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 7 allows remote attackers to cause a security certificate from a secure web site to appear invalid via a link to res://ieframe.dll/invalidcert.htm with the target site as an argument, which displays the site's URL in the address bar but causes Internet Explorer to report that the certificate is invalid.
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Analysis
by VulDB Data Team • 04/27/2026
This vulnerability in Microsoft Internet Explorer 7 represents a sophisticated phishing attack vector that exploits the browser's certificate validation display mechanism. The flaw resides in how Internet Explorer processes certificate warnings when users navigate to secure websites through specially crafted links. Attackers can leverage this weakness by creating malicious links that point to the res://ieframe.dll/invalidcert.htm resource with a target website URL as an argument. This technique allows adversaries to manipulate the browser's security indicators in a way that deceives users into believing they are visiting a legitimate secure site while actually displaying a certificate validation error.
The technical implementation of this vulnerability stems from Internet Explorer's handling of the resource protocol and its certificate validation user interface. When a user clicks on the crafted link, the browser loads the invalidcert.htm resource from the ieframe.dll module and passes the target URL as a parameter. The browser then displays the legitimate website address in the address bar while simultaneously showing a certificate error message. This creates a false sense of security where users see the correct domain name but are misled by the certificate warning, making it extremely difficult to distinguish between legitimate security warnings and malicious deception attempts. The vulnerability specifically affects the visual presentation and user trust indicators rather than actual cryptographic certificate validation, making it particularly dangerous for social engineering attacks.
The operational impact of this vulnerability extends beyond simple phishing scenarios to encompass broader security implications for web browsing trust models. Users may be tricked into believing they are on a legitimate secure website when they are actually encountering a malicious site that has been designed to mimic the appearance of a trusted entity. This manipulation of security indicators undermines the fundamental security model that users rely upon when browsing the internet, as the visual cues that should warn users about potential security threats are being subverted. The vulnerability affects all versions of Internet Explorer 7 that are configured to display certificate warnings, making it particularly dangerous in enterprise environments where users may be browsing with default security settings. According to CWE-611, this represents an insecure reference to a resource, while the ATT&CK technique T1566.001 covers the use of phishing for initial access through malicious web content.
The mitigation strategies for this vulnerability focus on both immediate browser-level fixes and broader security awareness measures. Microsoft released patches that addressed the core issue by modifying how Internet Explorer handles certificate warnings and resource loading from the ieframe.dll module. Organizations should ensure that all Internet Explorer 7 installations are updated with the latest security patches, though it's worth noting that Internet Explorer 7 reached end-of-life in 2014, making this vulnerability largely obsolete in modern environments. For legacy systems that cannot be upgraded, implementing additional security measures such as enhanced browser security policies, network-based filtering solutions, and user education programs becomes critical. The vulnerability highlights the importance of maintaining current browser versions and security updates, as older browsers often contain unpatched vulnerabilities that can be exploited in sophisticated attacks. Security professionals should also consider implementing network-level monitoring to detect and block suspicious resource protocol usage patterns that may indicate attempts to exploit similar vulnerabilities.