CVE-2001-1547 in Outlook Express
Summary
by MITRE
Outlook Express 6.0, with "Do not allow attachments to be saved or opened that could potentially be a virus" enabled, does not block email attachments from forwarded messages, which could allow remote attackers to execute arbitrary code.
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Analysis
by VulDB Data Team • 04/11/2019
This vulnerability exists in Microsoft Outlook Express 6.0 where the security feature designed to prevent potentially malicious email attachments from being saved or opened fails to properly validate forwarded messages. When the "Do not allow attachments to be saved or opened that could potentially be a virus" setting is enabled, the application incorrectly processes forwarded emails, bypassing the intended protection mechanisms. The flaw stems from the application's insufficient input validation and attachment handling logic when processing messages that have been forwarded through the email client. Attackers can exploit this by crafting malicious email attachments and forwarding them to victims who have this security setting enabled, effectively circumventing the protection measures that should prevent execution of potentially harmful code.
The technical implementation of this vulnerability involves a failure in the email processing pipeline where forwarded messages are not subjected to the same attachment validation checks as directly received messages. This represents a classic case of inadequate access control and input sanitization, aligning with CWE-20 - Improper Input Validation. The vulnerability allows for privilege escalation and arbitrary code execution on the victim's system, as the forwarded attachments bypass the security restrictions that normally prevent potentially malicious files from being executed or saved. The flaw operates at the application layer where email clients process and validate attachments, demonstrating poor security design in the context of email security protocols.
The operational impact of this vulnerability is significant as it undermines the security posture of users who rely on Outlook Express 6.0 for email communication. Attackers can leverage this weakness to deliver malware through seemingly legitimate forwarded emails, exploiting the trust relationship between users and the email client. This creates a vector for phishing attacks, malware distribution, and potentially more sophisticated social engineering campaigns. The vulnerability affects users who have enabled the security setting in question, making it particularly dangerous as it exploits the very protection mechanism that users expect to provide security. The attack requires minimal sophistication and can be executed through standard email forwarding mechanisms, making it a particularly effective exploit for threat actors.
Mitigation strategies for this vulnerability include immediate patching of Outlook Express 6.0 through Microsoft security updates, disabling the problematic security setting if possible, and implementing additional email filtering solutions at the network level. Organizations should also consider deploying email security appliances and advanced threat protection systems that can detect and block malicious attachments regardless of client-side security settings. Network administrators should implement email content filtering and sandboxing solutions to analyze suspicious attachments before they reach end users. The vulnerability highlights the importance of comprehensive security testing and validation of security features, particularly those that rely on user configuration settings. This case demonstrates the critical need for layered security approaches and the dangers of over-reliance on single-point security controls. From an ATT&CK framework perspective, this vulnerability maps to T1193 - Spearphishing Attachment and T1059 - Command and Scripting Interpreter, representing both initial access and execution phases of a typical attack lifecycle.