CVE-2008-1448 in Internet Explorer
Summary
by MITRE
The MHTML protocol handler in a component of Microsoft Outlook Express 5.5 SP2 and 6 through SP1, and Windows Mail, does not assign the correct Internet Explorer Security Zone to UNC share pathnames, which allows remote attackers to bypass intended access restrictions and read arbitrary files via an mhtml: URI in conjunction with a redirection, aka "URL Parsing Cross-Domain Information Disclosure Vulnerability."
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Analysis
by VulDB Data Team • 06/01/2025
The vulnerability described in CVE-2008-1448 represents a critical security flaw in Microsoft Outlook Express and Windows Mail applications that stems from improper handling of MHTML protocol URIs. This issue specifically affects Outlook Express 5.5 SP2 and 6 through SP1 versions, as well as Windows Mail, where the MHTML protocol handler fails to correctly assign Internet Explorer security zones to UNC share pathnames. The flaw creates a cross-domain information disclosure vulnerability that enables attackers to bypass intended access restrictions and gain unauthorized access to arbitrary files on the system.
The technical implementation of this vulnerability exploits the inconsistent security zone assignment mechanism within the MHTML protocol handler. When processing mhtml: URIs that contain redirections to UNC share pathnames, the system fails to properly evaluate the security context of these paths, allowing them to be treated as if they belong to a less restrictive security zone than they actually should. This misclassification enables attackers to leverage the vulnerability through carefully crafted malicious MHTML documents that redirect to network shares or local file paths, effectively circumventing the normal security boundaries that would otherwise prevent such access.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with the capability to access sensitive files that should normally be restricted to specific users or security contexts. Attackers can construct malicious MHTML documents that contain redirections to UNC shares or local file systems, exploiting the flawed zone assignment to gain unauthorized access to files that may contain confidential information, credentials, or system data. This vulnerability particularly affects environments where users have access to network shares or where sensitive data is stored on local systems that are not properly isolated from user-accessible applications.
Security researchers have categorized this vulnerability under CWE-200, which deals with Information Exposure, and it aligns with ATT&CK technique T1059.005 for Command and Scripting Interpreter, as it enables attackers to execute arbitrary file access operations through malicious MHTML content. The vulnerability demonstrates a classic case of improper input validation and security zone handling, where the application fails to properly validate the security context of URI redirections. Organizations should implement immediate mitigations including disabling MHTML protocol handling, updating to patched versions of affected software, and implementing network segmentation to limit access to sensitive shares. Additionally, user education regarding the dangers of opening suspicious email attachments and the importance of maintaining up-to-date security patches remains crucial in preventing exploitation of this vulnerability. The flaw underscores the importance of proper security zone assignment in web-based applications and highlights the risks associated with protocol handlers that do not properly validate the security context of their inputs.