CVE-2007-2227 in Outlook Express
Summary
by MITRE
The MHTML protocol handler in Microsoft Outlook Express 6 and Windows Mail in Windows Vista does not properly handle Content-Disposition "notifications," which allows remote attackers to obtain sensitive information from other Internet Explorer domains, aka "Content Disposition Parsing Cross Domain Information Disclosure Vulnerability."
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Analysis
by VulDB Data Team • 06/22/2025
The vulnerability identified as CVE-2007-2227 represents a critical information disclosure flaw within the MHTML protocol handler of Microsoft Outlook Express 6 and Windows Mail applications running on Windows Vista systems. This weakness stems from improper handling of Content-Disposition headers, specifically those designated for notifications, creating a cross-domain information disclosure scenario that exposes sensitive data across different internet domains. The vulnerability operates at the protocol level where the affected applications fail to properly validate and process MIME content disposition parameters, allowing malicious actors to exploit this gap in security implementation. This issue directly impacts the security boundaries that separate different web domains and browsers, potentially enabling attackers to access confidential information that should remain isolated within specific domain contexts.
The technical exploitation of this vulnerability occurs when the affected applications process MHTML content that contains specially crafted Content-Disposition headers with notification directives. The MHTML protocol handler in these Microsoft applications does not adequately sanitize or validate the disposition parameters, leading to improper parsing of the notification content. This parsing error creates a scenario where the application's security model is bypassed, allowing information to flow from one domain context to another without proper authorization. The flaw specifically manifests when the system encounters Content-Disposition headers that specify notification behavior, which should normally be handled differently from regular content processing. According to CWE classification, this vulnerability maps to CWE-200, which describes improper output neutralization for logs, and CWE-201, which covers improper handling of information flow. The vulnerability also aligns with ATT&CK technique T1071.004, which covers application layer protocol: web protocols, specifically targeting the improper handling of web content in email clients.
The operational impact of this vulnerability extends beyond simple information disclosure, as it compromises the fundamental security model of web browsing and email processing. Attackers can leverage this weakness to extract sensitive data from other domains, potentially accessing cookies, session information, or other confidential data that should remain protected within specific domain boundaries. The vulnerability affects not only the email client itself but also creates potential pathways for further attacks, as the leaked information could be used to construct more sophisticated exploitation techniques. In enterprise environments, this could result in unauthorized access to internal communications, user credentials, or business-sensitive information that crosses domain boundaries. The exposure of cross-domain information creates a significant risk for organizations relying on these email applications, as it undermines the isolation mechanisms that protect against cross-site scripting attacks and other information leakage scenarios.
Mitigation strategies for CVE-2007-2227 should focus on both immediate remediation and long-term security improvements. Microsoft released patches addressing this vulnerability through security updates, but organizations should ensure all affected systems receive proper patching. Additional protective measures include implementing strict email content filtering, disabling MHTML processing in email clients, and configuring security policies that restrict cross-domain information flow. Network-level protections such as web application firewalls and content filtering systems can help detect and block malicious MHTML content. Security teams should also consider implementing monitoring for unusual cross-domain data access patterns and establish incident response procedures for potential exploitation attempts. The vulnerability highlights the importance of proper input validation and the need for robust protocol handling in email clients, particularly when processing complex MIME content types that may contain embedded security risks. Organizations should also review their email security configurations and ensure that legacy applications like Outlook Express are either properly patched or decommissioned to prevent exploitation of this and similar vulnerabilities.