CVE-2013-3930 in FTP
Summary
by MITRE
Stack-based buffer overflow in Core FTP before 2.2 build 1785 allows remote FTP servers to execute arbitrary code via a crafted directory name in a CWD command reply.
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Analysis
by VulDB Data Team • 05/09/2026
The vulnerability identified as CVE-2013-3930 represents a critical stack-based buffer overflow flaw within Core FTP client software versions prior to build 2.2.1785. This vulnerability specifically manifests when the client processes directory names in response to CWD (Change Working Directory) commands from remote FTP servers. The flaw occurs because the application fails to properly validate or limit the length of directory names received during FTP session operations, creating an exploitable condition where maliciously crafted directory names can overflow the allocated stack buffer. Such buffer overflow conditions are particularly dangerous as they can be leveraged by remote attackers to overwrite adjacent memory locations including return addresses and control data, potentially enabling arbitrary code execution. The vulnerability stems from inadequate input validation mechanisms within the FTP client's command processing logic, where the application assumes directory names will not exceed predetermined length limits without implementing proper bounds checking.
The technical exploitation of this vulnerability requires a remote FTP server to send a specially crafted CWD command reply containing an excessively long directory name that exceeds the buffer allocation size. When the Core FTP client attempts to process this malformed directory name, the stack buffer overflow occurs, potentially allowing an attacker to inject and execute malicious code with the privileges of the affected user. This type of vulnerability maps directly to CWE-121 Stack-based Buffer Overflow, which is classified under the Common Weakness Enumeration framework as a fundamental flaw in memory management where data written to a buffer extends beyond its allocated bounds. The attack vector is remote and requires no authentication from the victim, making it particularly concerning for networked environments where users might unknowingly connect to malicious FTP servers. The vulnerability is classified under the MITRE ATT&CK framework as part of the 'Exploitation for Client Execution' tactic, where adversaries leverage client-side vulnerabilities to execute arbitrary code.
The operational impact of this vulnerability extends beyond simple code execution as it can lead to complete system compromise when exploited successfully. An attacker who successfully exploits this vulnerability gains the ability to execute arbitrary commands on the victim's system, potentially leading to data theft, system infiltration, or further network propagation. The vulnerability affects all versions of Core FTP client prior to build 2.2.1785, making it a widespread concern for organizations that have not updated their FTP client software. The attack scenario typically involves a victim connecting to a malicious FTP server that has been configured to send the crafted CWD command reply, requiring minimal user interaction beyond initiating the FTP connection. This makes the vulnerability particularly dangerous in environments where users frequently connect to external FTP servers or where automated FTP clients are used in enterprise environments. The potential for privilege escalation and lateral movement within networks makes this vulnerability a significant concern for security professionals managing endpoint protection.
The recommended mitigations for CVE-2013-3930 focus primarily on immediate software updates and patches provided by the vendor. Organizations should immediately upgrade to Core FTP build 2.2.1785 or later versions that contain the necessary fixes for the buffer overflow vulnerability. Additionally, network administrators should implement firewall rules and access controls to limit exposure to potentially malicious FTP servers, particularly when users are required to connect to external FTP resources. Security monitoring should include detection of unusual FTP activity patterns and malformed directory names that could indicate exploitation attempts. The vulnerability also highlights the importance of secure coding practices including input validation, bounds checking, and proper memory management in client applications. Organizations should consider implementing network segmentation and user access controls to limit the potential impact of successful exploitation, while also maintaining regular vulnerability assessments to identify similar issues in other client applications. The remediation process should also include user education regarding the risks of connecting to untrusted FTP servers and the importance of keeping software updated to address known security vulnerabilities.