CVE-2006-2111 in Internet Explorer
Summary
by MITRE
A component in Microsoft Outlook Express 6 allows remote attackers to bypass domain restrictions and obtain sensitive information via redirections with the mhtml: URI handler, as originally reported for Internet Explorer 6 and 7, aka "URL Redirect Cross Domain Information Disclosure Vulnerability."
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Analysis
by VulDB Data Team • 01/20/2025
The vulnerability identified as CVE-2006-2111 represents a critical cross-domain information disclosure flaw affecting Microsoft Outlook Express 6 and Internet Explorer 6 and 7. This security weakness stems from the improper handling of mhtml: URI schemes within the affected applications, creating a pathway for malicious actors to circumvent domain restriction mechanisms that are typically enforced by web browsers and email clients. The vulnerability specifically exploits the way these applications process redirections when encountering mhtml: protocol handlers, allowing attackers to retrieve sensitive information from different domains than those explicitly permitted by the security policies. This flaw operates at the intersection of web browser security models and email client processing, creating a unique attack vector that leverages the trust relationships between different protocol handlers.
The technical implementation of this vulnerability involves the manipulation of URI schemes and redirection mechanisms within the affected Microsoft applications. When Outlook Express 6 processes email messages containing mhtml: URIs that redirect to different domains, the application fails to properly enforce domain-based security restrictions that would normally prevent access to resources outside the originating domain. This behavior creates a bypass of the same-origin policy that is fundamental to web security models, allowing attackers to craft malicious email content that, when processed by the vulnerable client, can retrieve information from arbitrary domains. The vulnerability is particularly concerning because it affects both email client and web browser components, expanding the potential attack surface and attack vectors available to threat actors.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables attackers to perform cross-domain reconnaissance and potentially extract sensitive data from targeted systems. Security researchers have documented how this vulnerability can be exploited to access resources that would normally be restricted by domain policies, including potentially sensitive information that might be accessible through different domains within the same organization. The attack requires minimal user interaction, as simply opening a malicious email message containing the crafted mhtml: URI redirections can trigger the vulnerability. This makes the exploit particularly dangerous in enterprise environments where email-based attacks are common and where users may not be adequately trained to identify suspicious email content.
Mitigation strategies for this vulnerability require a multi-layered approach combining application-level patches, network-level controls, and user awareness training. Microsoft addressed this issue through security updates that modified how mhtml: URI handlers are processed, ensuring that proper domain restrictions are enforced even during redirection scenarios. Organizations should implement strict email filtering policies that can detect and block malicious mhtml: URI patterns, particularly in enterprise email environments where the attack surface is larger. The vulnerability aligns with CWE-200, which describes improper output neutralization for logs and other security artifacts, and can be mapped to ATT&CK technique T1190, which covers exploit public-facing application. Network administrators should also consider implementing web application firewalls and content filtering solutions that can detect and block suspicious URI redirection patterns. Additionally, regular security awareness training for users helps reduce the risk of successful exploitation through social engineering components that might be used in conjunction with this technical vulnerability.