CVE-2000-0567 in Outlook
Summary
by MITRE
Buffer overflow in Microsoft Outlook and Outlook Express allows remote attackers to execute arbitrary commands via a long Date field in an email header, aka the "Malformed E-mail Header" vulnerability.
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Analysis
by VulDB Data Team • 05/31/2025
The CVE-2000-0567 vulnerability represents a critical buffer overflow flaw affecting Microsoft Outlook and Outlook Express email clients. This vulnerability specifically targets the handling of email header fields, particularly the Date field, where maliciously crafted long strings can trigger memory corruption. The flaw exists in the email parsing logic that fails to properly validate input length before copying data into fixed-size memory buffers. When a victim receives an email containing an excessively long Date header field, the email client attempts to process this malformed data without adequate bounds checking, leading to buffer overflow conditions that can be exploited by remote attackers.
The technical implementation of this vulnerability stems from improper input validation mechanisms within Microsoft's email processing libraries. The Date field in email headers is typically expected to follow standard formats such as RFC 822 or RFC 2822 specifications, but the vulnerable implementations fail to enforce reasonable length limits for this field. When an attacker crafts an email with a Date header exceeding the allocated buffer size, typically 256 or 512 bytes depending on the specific implementation, the overflow occurs during parsing operations. This memory corruption can overwrite adjacent memory locations including return addresses, function pointers, or other critical program state information, providing attackers with the opportunity to execute arbitrary code with the privileges of the affected email client process.
The operational impact of CVE-2000-0567 extends beyond simple remote code execution to encompass potential system compromise and data exfiltration capabilities. Since Outlook and Outlook Express are widely deployed email clients, the vulnerability presents a significant attack surface for threat actors seeking to compromise end-user systems. The remote nature of the exploit means that attackers can initiate attacks without requiring physical access to target systems, making this vulnerability particularly dangerous in enterprise environments where email is a primary communication channel. Successful exploitation can result in full system compromise, allowing attackers to establish persistent backdoors, harvest credentials, or deploy additional malware payloads. The vulnerability also poses risks to email server infrastructure if the clients are used to process emails from untrusted sources, potentially enabling attackers to gain unauthorized access to corporate email systems.
Mitigation strategies for CVE-2000-0567 should focus on both immediate protective measures and long-term architectural improvements. Microsoft released patches addressing this vulnerability through security updates, but organizations should also implement email filtering solutions that can detect and block malformed email headers before they reach end-user clients. Network-based intrusion detection systems should be configured to monitor for suspicious email traffic patterns that might indicate exploitation attempts. Additionally, security configurations should include disabling unnecessary email client features, implementing strict input validation policies, and regularly updating email client software to address known vulnerabilities. The vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and maps to ATT&CK technique T1190 for exploitation of remote services and T1059 for command and scripting interpreter usage, highlighting the multi-faceted nature of the threat landscape this vulnerability creates. Organizations should also consider implementing email security gateways that can sanitize headers and validate email format compliance before delivery to client systems.