CVE-2018-18861 in FTP Server
Summary
by MITRE
Buffer overflow in PCMan FTP Server 2.0.7 allows for remote code execution via the APPE command.
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Analysis
by VulDB Data Team • 06/11/2023
The vulnerability identified as CVE-2018-18861 represents a critical buffer overflow flaw within PCMan FTP Server version 2.0.7 that exposes systems to remote code execution attacks. This issue specifically manifests through the APPE command implementation, which fails to properly validate input lengths before processing user-supplied data. The buffer overflow occurs when the server receives a malformed APPE command containing excessive data, causing memory corruption that can be exploited by malicious actors to execute arbitrary code on the affected system. The vulnerability demonstrates characteristics consistent with CWE-121, which describes stack-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations. This type of flaw directly aligns with ATT&CK technique T1059.007, which involves the execution of commands through the use of a command and scripting interpreter, as attackers can leverage the buffer overflow to inject and execute malicious payloads.
The operational impact of this vulnerability extends beyond simple remote code execution to encompass complete system compromise and potential lateral movement within network environments. When exploited successfully, the buffer overflow enables attackers to gain unauthorized access to the server's operating system with the privileges of the running FTP service, which typically operates with elevated permissions. The attack vector requires only network connectivity to the FTP server, making it particularly dangerous as it can be exploited from external networks without requiring physical access or prior authentication. The vulnerability affects systems running PCMan FTP Server 2.0.7 and potentially earlier versions, creating a widespread risk across organizations that have not updated their FTP server implementations. Security researchers have noted that the exploitation process often involves crafting specific payloads that trigger the buffer overflow condition during command processing, making this attack relatively straightforward for skilled adversaries to implement.
Mitigation strategies for CVE-2018-18861 should prioritize immediate patching of affected systems, as the vendor has released updates addressing the buffer overflow vulnerability. Organizations should implement network segmentation to limit exposure of FTP services to untrusted networks and consider disabling unnecessary FTP functionality where possible. The implementation of intrusion detection systems can help identify exploitation attempts by monitoring for anomalous APPE command usage patterns, while network access control lists should restrict FTP server access to authorized users only. Security administrators should also consider implementing additional layers of protection such as FTP server hardening measures, including disabling unused commands and implementing strict input validation. The vulnerability highlights the importance of maintaining up-to-date software implementations and following security best practices for network services, particularly those that handle user input without proper sanitization. Organizations should conduct comprehensive vulnerability assessments to identify all instances of PCMan FTP Server within their environments and ensure complete remediation through official patches or service replacement. Additionally, monitoring for suspicious FTP activity and implementing automated security controls can help prevent exploitation attempts and reduce the risk of successful attacks against vulnerable systems.