CVE-2013-4730 in FTP Server
Summary
by MITRE
Buffer overflow in PCMan s FTP Server 2.0.7 allows remote attackers to execute arbitrary code via a long string in a USER command.
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Analysis
by VulDB Data Team • 07/03/2025
The vulnerability identified as CVE-2013-4730 represents a critical buffer overflow flaw in PCMan FTP Server version 2.0.7 that exposes remote attackers to potential code execution capabilities. This issue stems from inadequate input validation within the server's USER command processing mechanism, where the application fails to properly sanitize user-supplied data before storing it in a fixed-length buffer. The flaw specifically manifests when a maliciously crafted string exceeds the allocated buffer space, causing adjacent memory locations to be overwritten with attacker-controlled data. Such buffer overflow conditions create exploitable conditions that can be leveraged to manipulate program execution flow and ultimately achieve remote code execution on the affected system. The vulnerability affects the core authentication process of the FTP server, making it particularly dangerous as it can be exploited during initial connection attempts without requiring prior authentication.
The technical implementation of this vulnerability aligns with CWE-121, which categorizes buffer overflow conditions occurring in stack-based buffers, and specifically relates to CWE-787, which addresses out-of-bounds write operations. The attack vector operates through the standard FTP protocol communication where the USER command serves as the entry point for exploitation. When an attacker sends a specially crafted USER command containing an excessively long string, the server's handling routine fails to validate the input length against the buffer capacity, resulting in memory corruption. This memory corruption can overwrite critical program control data such as return addresses, function pointers, or stack canaries, enabling attackers to redirect program execution to malicious code injected into the buffer. The vulnerability demonstrates characteristics consistent with stack-based buffer overflows that are commonly classified under the ATT&CK technique T1203 - Exploitation for Client Execution, where adversaries leverage software vulnerabilities to execute malicious code on target systems.
The operational impact of CVE-2013-4730 extends beyond simple remote code execution to encompass complete system compromise and potential lateral movement within network environments. An attacker exploiting this vulnerability can gain unauthorized access to the affected FTP server and potentially escalate privileges to the system level, depending on the server's execution context and user permissions. The vulnerability's remote nature means that attackers can exploit it from anywhere on the network without requiring physical access or local system credentials, making it particularly attractive for automated exploitation campaigns. Additionally, since FTP servers often serve as critical infrastructure components for file sharing and data transfer operations, successful exploitation can lead to data breaches, system hijacking, and disruption of legitimate business operations. The vulnerability also poses risks to network security monitoring systems, as the exploitation may generate traffic patterns that could evade detection by traditional signature-based intrusion detection systems.
Mitigation strategies for CVE-2013-4730 should focus on immediate remediation through software updates and patches provided by the vendor, as well as implementing network-level protections to prevent unauthorized access. Organizations should prioritize patch management procedures to ensure all instances of PCMan FTP Server are updated to versions that address this vulnerability, typically through version 2.0.8 or later releases. Network segmentation and firewall rules should be implemented to restrict access to FTP services to only trusted internal networks, while disabling unnecessary FTP services on public-facing systems. Additional defensive measures include implementing intrusion detection systems with signature updates that can detect exploitation attempts, monitoring for unusual USER command patterns, and deploying application-level firewalls or web application firewalls that can filter malicious input. System hardening practices such as disabling unnecessary services, implementing proper access controls, and regularly auditing system configurations should also be employed. The vulnerability highlights the importance of input validation and proper memory management practices in server-side applications, as recommended by the OWASP Top Ten and other security frameworks that emphasize the need for secure coding practices to prevent such memory corruption vulnerabilities.