CVE-2006-2107 in SMTP Server
Summary
by MITRE
Buffer overflow in BL4 SMTP Server 0.1.4 and earlier allows remote attackers to cause a denial of service (crash) or execute arbitrary code via a long argument to the (1) EHLO, (2) MAIL FROM, and (3) RCPT TO commands.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 03/26/2019
The vulnerability identified as CVE-2006-2107 represents a critical buffer overflow flaw in BL4 SMTP Server version 0.1.4 and earlier implementations. This security defect manifests within the server's handling of specific SMTP commands, creating a pathway for remote attackers to exploit the system's memory management weaknesses. The vulnerability specifically targets three fundamental SMTP commands that are essential for email transmission processes, making it particularly dangerous as it can disrupt core email services while potentially enabling code execution.
The technical nature of this buffer overflow stems from insufficient input validation within the BL4 SMTP Server's command processing routines. When the server receives a malformed argument exceeding predetermined buffer limits during EHLO, MAIL FROM, or RCPT TO command execution, the excess data overflows into adjacent memory segments. This overflow condition occurs because the application fails to properly bounds-check user-supplied input before copying it into fixed-size memory buffers. The flaw directly maps to CWE-121, which describes stack-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations.
The operational impact of this vulnerability extends beyond simple service disruption to encompass potential system compromise. Remote attackers can leverage this weakness to trigger denial of service conditions that cause the SMTP server to crash and restart, effectively disrupting email services for legitimate users. More critically, the buffer overflow could be weaponized to execute arbitrary code with the privileges of the SMTP server process, potentially allowing attackers to gain unauthorized access to the underlying system. This represents a significant escalation from simple DoS to full system compromise, making the vulnerability particularly attractive to malicious actors.
The attack vector for this vulnerability requires remote access to the SMTP server port, typically port 25, and involves crafting specially formatted SMTP commands with excessively long arguments. The exploitation process does not require authentication, making it accessible to anyone who can connect to the vulnerable server. This characteristic aligns with ATT&CK technique T1190, which describes the use of external remote services for initial access and persistence. The vulnerability affects organizations that deploy the BL4 SMTP Server in production environments, particularly those without proper network segmentation or intrusion detection measures.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term security posture improvements. The primary recommendation involves upgrading to a patched version of the BL4 SMTP Server or migrating to a more robust mail server implementation that properly handles input validation. Organizations should implement network segmentation to limit exposure of SMTP services to untrusted networks and deploy intrusion prevention systems capable of detecting malformed SMTP traffic patterns. Additionally, regular security assessments and vulnerability scanning should be conducted to identify similar issues in other network services. The remediation process should also include implementing proper input validation controls and following secure coding practices that prevent buffer overflow conditions through techniques such as stack canaries, address space layout randomization, and compiler-based protections.