CVE-2005-0636 in Foxmail Email Server
Summary
by MITRE
Format string vulnerability in Foxmail Server 2.0 allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via format strings in the USER command.
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Analysis
by VulDB Data Team • 03/26/2019
The vulnerability identified as CVE-2005-0636 represents a critical format string flaw in Foxmail Server 2.0 that exposes the system to remote exploitation. This issue specifically affects the handling of user commands, particularly the USER command which is fundamental to the mail server's authentication process. The vulnerability stems from improper input validation and sanitization within the server's command processing logic, creating a pathway for malicious actors to manipulate memory structures through crafted format specifiers. The flaw exists at the application layer and demonstrates a classic security weakness that has been documented in numerous systems over the years, with the Common Weakness Enumeration cataloguing this as CWE-134, which describes the use of format strings inappropriately. The vulnerability's impact extends beyond simple denial of service to potentially enabling arbitrary code execution, making it a severe concern for organizations relying on the affected mail server software.
The technical exploitation of this vulnerability occurs when an attacker sends a specially crafted USER command containing format string specifiers such as %x, %s, or %n to the Foxmail Server. These specifiers can cause the application to read from or write to memory locations that are not properly validated, leading to stack corruption, memory access violations, or potentially code execution. The server's failure to properly sanitize user input before processing it through format string functions creates a direct attack surface that can be leveraged by remote threat actors. When the server attempts to process the malformed input, it interprets the format specifiers as instructions for memory operations rather than literal text, causing the application to behave unpredictably and potentially crash or execute unintended code. This type of vulnerability is particularly dangerous because it can be exploited without requiring authentication, making it a prime target for automated exploitation tools and widespread attacks.
The operational impact of this vulnerability extends beyond immediate service disruption to potentially compromise the entire mail server infrastructure. Organizations utilizing Foxmail Server 2.0 face significant risk of unauthorized access, data breaches, and complete system compromise if the vulnerability is exploited successfully. The potential for arbitrary code execution means that attackers could gain full control over the server, allowing them to install backdoors, exfiltrate sensitive email data, or use the compromised server as a launching point for further attacks within the network. The vulnerability affects the server's ability to properly authenticate users and process mail commands, leading to both denial of service conditions and potential data exposure. According to the ATT&CK framework, this vulnerability maps to techniques involving command injection and privilege escalation, making it a valuable target for threat actors seeking to establish persistent access to email infrastructure. The impact is particularly severe in enterprise environments where mail servers serve as critical communication infrastructure, and the vulnerability could lead to cascading failures throughout the organization's digital ecosystem.
Mitigation strategies for CVE-2005-0636 require immediate action from system administrators and security teams to protect their mail server infrastructure. The primary recommendation involves applying the vendor-provided security patches or upgrading to a newer version of Foxmail Server that addresses the format string vulnerability. Organizations should also implement network segmentation and access controls to limit exposure of the mail server to untrusted networks. Input validation measures should be enhanced to filter out potentially malicious format specifiers in all user commands, particularly those that are processed by the server's authentication mechanisms. Security monitoring should be implemented to detect unusual patterns in USER command usage that might indicate exploitation attempts. Additionally, system administrators should consider disabling unnecessary mail server functions and implementing proper logging and alerting mechanisms to quickly identify and respond to potential exploitation attempts. The vulnerability highlights the importance of regular security assessments and vulnerability management processes, as it demonstrates how legacy software can contain critical security flaws that remain unpatched for extended periods. Organizations should also consider implementing intrusion detection systems that can identify and block known exploit patterns for this type of vulnerability, as well as establishing incident response procedures specifically tailored to address format string vulnerabilities in mail server environments.