CVE-2004-2417 in smtp.proxy
Summary
by MITRE
Format string vulnerability in smtp.c for smtp.proxy 1.1.3 and earlier allows remote attackers to execute arbitrary code via format string specifiers in the (1) client hostname or (2) message-id, which are injected into a syslog message.
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Analysis
by VulDB Data Team • 06/29/2018
This vulnerability exists in the smtp.proxy software version 1.1.3 and earlier, specifically within the smtp.c component where improper input validation leads to a format string vulnerability. The flaw occurs when the application processes client hostname or message-id values that are directly incorporated into syslog messages without proper sanitization or formatting. Attackers can exploit this by crafting malicious input containing format specifiers such as %s, %x, or %n that are interpreted by the printf family of functions during syslog logging operations. This vulnerability falls under the Common Weakness Enumeration category CWE-134 which specifically addresses the use of format strings in logging functions without proper validation, making it a critical security flaw that can be leveraged for remote code execution.
The technical exploitation of this vulnerability allows remote attackers to inject malicious format specifiers into the syslog message logging process. When the smtp.proxy application receives a client hostname or message-id containing format string specifiers, these values are directly passed to syslog functions that use printf-style formatting. This creates opportunities for attackers to perform memory reads, writes, or even execute arbitrary code by manipulating the stack through format string exploitation techniques. The vulnerability is particularly dangerous because it allows attackers to inject code execution primitives that can be used to gain control over the affected system. The attack vector is remote and does not require authentication, making it especially severe in networked environments where the smtp.proxy service is exposed to untrusted networks.
The operational impact of this vulnerability extends beyond simple code execution, as it can enable attackers to perform various malicious activities including privilege escalation, data exfiltration, and system compromise. The syslog message injection point provides attackers with a reliable method to manipulate the application's behavior and potentially gain unauthorized access to system resources. This vulnerability also affects system logging integrity, as attackers can manipulate log entries to hide their activities or create false audit trails. The attack can be particularly devastating in environments where smtp.proxy is used as a mail relay or gateway, as it could allow unauthorized users to execute commands on the mail server with the privileges of the running process. Organizations relying on this software for email services face significant risk of unauthorized access and potential data breaches.
Mitigation strategies for this vulnerability should focus on immediate patching of the smtp.proxy software to version 1.1.4 or later, which contains the necessary fixes for the format string handling. System administrators should implement input validation and sanitization measures to prevent format specifiers from being passed directly to logging functions. The recommended approach includes using safe string formatting functions such as snprintf instead of sprintf, and implementing proper escape sequences for user-supplied data before logging. Network segmentation and firewall rules should be configured to limit access to the smtp.proxy service to trusted sources only. Additionally, monitoring and alerting should be implemented to detect potential exploitation attempts through unusual syslog entries or network traffic patterns. Organizations should also consider implementing intrusion detection systems that can identify format string exploitation attempts and maintain comprehensive backup and recovery procedures to quickly restore systems in case of successful compromise. This vulnerability demonstrates the critical importance of proper input validation and secure coding practices in network services, particularly those that handle user-supplied data in logging contexts.