CVE-2006-3277 in Mailenable Professional
Summary
by MITRE
The SMTP service of MailEnable Standard 1.92 and earlier, Professional 2.0 and earlier, and Enterprise 2.0 and earlier before the MESMTPC hotfix, allows remote attackers to cause a denial of service (application crash) via a HELO command with a null byte in the argument, possibly triggering a length inconsistency or a missing argument.
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Analysis
by VulDB Data Team • 06/22/2019
The vulnerability described in CVE-2006-3277 represents a critical denial of service flaw affecting MailEnable SMTP services across multiple product versions including Standard 1.92 and earlier, Professional 2.0 and earlier, and Enterprise 2.0 and earlier. This vulnerability specifically targets the SMTP service implementation within the MailEnable email server software, which is widely deployed in enterprise email environments. The issue manifests when the SMTP service receives a HELO command containing a null byte within its argument, creating a condition that can lead to application instability and complete service disruption.
The technical root cause of this vulnerability lies in the improper handling of input validation within the SMTP service's command processing logic. When a remote attacker sends a HELO command with a null byte embedded in the argument, the service fails to properly validate or sanitize the input before processing it. This flaw falls under CWE-129, Input Validation, and specifically relates to improper handling of special characters and null bytes in command arguments. The null byte injection causes the application to experience a length inconsistency where the internal string processing functions encounter unexpected termination characters, leading to memory corruption or buffer overflow conditions. The missing argument validation creates an opportunity for the service to interpret malformed input in an unpredictable manner, potentially causing memory access violations or stack corruption that results in application crashes.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be exploited by remote attackers without authentication to systematically disable email services. This denial of service condition affects email availability for organizations relying on MailEnable, potentially disrupting business communications and email-based workflows. The vulnerability is particularly concerning in enterprise environments where email infrastructure is critical for business operations, as it can be exploited to create service outages that may last until the affected service is manually restarted or the system is rebooted. Organizations using these older MailEnable versions face significant risk of service interruption, especially during peak email processing hours when the impact would be most detrimental to business operations.
Mitigation strategies for this vulnerability require immediate implementation of the MESMTPC hotfix provided by MailEnable to address the specific input validation flaw in the SMTP service. Organizations should also consider implementing network-level protections such as firewalls that can filter out malformed SMTP commands or limit access to the SMTP service to trusted networks only. Additionally, monitoring and logging of SMTP service activities should be enhanced to detect unusual command patterns that may indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation and the potential for seemingly benign input handling flaws to create severe operational impacts, aligning with ATT&CK technique T1499.004 for Network Denial of Service. System administrators should also consider implementing intrusion detection systems that can identify and alert on suspicious SMTP command sequences containing null bytes or other malformed input patterns that could indicate exploitation attempts.