CVE-2002-1179 in Outlook Express
Summary
by MITRE
Buffer overflow in the S/MIME Parsing capability in Microsoft Outlook Express 5.5 and 6.0 allows remote attackers to execute arbitrary code via a digitally signed email with a long "From" address, which triggers the overflow when the user views or previews the message.
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Analysis
by VulDB Data Team • 06/22/2025
The vulnerability described in CVE-2002-1179 represents a critical buffer overflow flaw within Microsoft Outlook Express versions 5.5 and 6.0 that specifically targets the S/MIME parsing functionality. This issue arises when the email client processes digitally signed messages containing excessively long "From" address fields, creating a condition where memory allocated for processing the address exceeds its designated bounds. The vulnerability operates at the application layer and demonstrates the classic characteristics of a stack-based buffer overflow that can be exploited through crafted email content.
The technical implementation of this vulnerability stems from inadequate input validation within the S/MIME parsing component of Outlook Express. When a user opens or previews a message containing an overly long "From" address field, the application fails to properly bounds-check the input data before copying it into fixed-size memory buffers. This allows attackers to overwrite adjacent memory locations with malicious data, potentially including executable code or jump instructions that redirect program execution flow. The flaw specifically affects the handling of digitally signed emails, making it particularly dangerous as users may be tricked into opening seemingly legitimate signed messages that contain the malicious payload.
The operational impact of this vulnerability extends beyond simple code execution, as it enables remote code execution without requiring user interaction beyond viewing the malicious email. Attackers can craft specially designed emails with extended "From" headers that trigger the buffer overflow when Outlook Express attempts to parse the S/MIME signature information. This creates a scenario where an attacker can remotely compromise a victim's system simply by sending a malicious email, with the potential for privilege escalation depending on the target system configuration. The vulnerability affects both Outlook Express 5.5 and 6.0, representing a significant security gap in Microsoft's email client software during that era.
From a cybersecurity perspective, this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and represents a classic example of how improper input validation can lead to arbitrary code execution. The attack vector follows the patterns described in MITRE ATT&CK framework under T1203, which covers exploitation of remote services and applications through crafted input. The vulnerability demonstrates how S/MIME signature processing can become a security attack surface when proper memory management practices are not implemented. Organizations using these affected versions of Outlook Express faced significant risk as the flaw could be exploited through social engineering campaigns targeting email users, making it particularly dangerous in enterprise environments where email communication is prevalent.
Mitigation strategies for this vulnerability required immediate patching through Microsoft security updates, as the flaw was not exploitable without user interaction in the form of viewing or previewing the malicious message. System administrators needed to ensure all affected Outlook Express installations were updated promptly, as the vulnerability could be exploited through various email delivery methods including webmail interfaces that might display S/MIME signatures. The incident highlighted the importance of proper memory management in email client applications and the need for comprehensive input validation, particularly when handling cryptographic signature data that could be manipulated by attackers to create buffer overflow conditions.