CVE-2005-2409 in nbsmtp
Summary
by MITRE
Format string vulnerability in util.c in nbsmtp 0.99 and earlier, while running in debug mode, allows remote attackers to execute arbitrary code via format string specifiers that are not properly handled in a syslog call.
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Analysis
by VulDB Data Team • 01/10/2025
The vulnerability identified as CVE-2005-2409 represents a critical format string vulnerability within the nbsmtp mail server software version 0.99 and earlier. This flaw exists specifically within the util.c source file and manifests when the application operates in debug mode, creating a significant security risk for systems that may be exposed to untrusted network traffic. The vulnerability stems from improper handling of format string specifiers in syslog calls, which allows remote attackers to inject malicious format specifiers that can lead to arbitrary code execution. The nbsmtp software is designed to handle email transmission and management, making it a potential target for attackers seeking to compromise mail server infrastructure. When the debug mode is enabled, the application becomes particularly vulnerable as it processes user-supplied data through syslog functions without proper validation or sanitization, creating an attack surface that can be exploited by malicious actors.
The technical exploitation of this vulnerability occurs through the manipulation of format string specifiers that are passed to syslog functions within the nbsmtp application. When debug mode is active, the software processes incoming data and passes it directly to syslog calls without proper input validation, which allows attackers to inject format specifiers such as %n, %s, or %x that can cause the application to read or write memory locations. This type of vulnerability falls under the Common Weakness Enumeration category CWE-134, which specifically addresses the use of format strings without proper validation. The attacker can leverage this weakness to perform memory corruption attacks, potentially leading to stack smashing or heap corruption that can be used to execute arbitrary code with the privileges of the running process. The vulnerability is particularly dangerous because it can be exploited remotely without requiring authentication, making it an attractive target for automated attacks or exploit kits targeting vulnerable mail servers.
The operational impact of CVE-2005-2409 extends beyond simple privilege escalation, as it can result in complete system compromise when attackers successfully exploit the format string vulnerability. An attacker who successfully exploits this vulnerability can gain arbitrary code execution capabilities, potentially allowing them to install backdoors, modify system files, or establish persistent access to the compromised mail server. The vulnerability affects organizations that deploy nbsmtp in debug mode, which may be common in development or testing environments where security hardening is not properly implemented. The attack vector is particularly concerning because it can be executed over the network without requiring any authentication, making it a significant threat to mail server infrastructure. Organizations using affected versions of nbsmtp should consider this vulnerability as part of their broader security posture assessment, especially when these systems are exposed to untrusted networks or internet-facing services. The vulnerability also aligns with ATT&CK technique T1059.007, which covers command and scripting interpreter usage, as successful exploitation could enable attackers to execute arbitrary commands on the compromised system.
Mitigation strategies for CVE-2005-2409 should focus on immediate patching of the affected nbsmtp software to version 1.00 or later, which contains the necessary fixes for the format string vulnerability. Organizations should disable debug mode on all production mail server instances, as this mode significantly increases the attack surface and exposes the system to this particular vulnerability. System administrators should implement proper input validation and sanitization practices, ensuring that all user-supplied data is properly escaped or encoded before being passed to syslog functions. Network segmentation and firewall rules should be configured to restrict access to mail server services, limiting exposure to only trusted networks and IP addresses. Additionally, organizations should conduct regular security assessments to identify any other applications or services that may be vulnerable to similar format string issues, as this type of vulnerability is not uncommon in legacy software implementations. Monitoring and logging should be enhanced to detect potential exploitation attempts, particularly around syslog function calls and unusual format string patterns that may indicate active exploitation attempts. The vulnerability also highlights the importance of following secure coding practices and implementing proper error handling mechanisms to prevent similar issues in future software development cycles.