CVE-2025-3371: Pcman Ftp Server Buffer Overflow Flaw

CVE-2025-3371 Overview

A critical buffer overflow vulnerability has been identified in PCMan FTP Server 2.0.7. This vulnerability affects the DELETE Command Handler component, where improper input validation allows attackers to manipulate input data, leading to a buffer overflow condition. The vulnerability can be exploited remotely over the network without requiring authentication, making it a significant security concern for organizations running affected versions of this FTP server software.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability in the DELETE Command Handler to potentially execute arbitrary code, cause denial of service, or compromise the integrity of the affected system.

Affected Products

• PCMan FTP Server 2.0.7
• pcman ftp_server (cpe:2.3:a:pcman:ftp_server:2.0.7:::::::*)

Discovery Timeline

• April 7, 2025 - CVE-2025-3371 published to NVD
• May 16, 2025 - Last updated in NVD database

Technical Details for CVE-2025-3371

Vulnerability Analysis

This vulnerability resides in the DELETE Command Handler component of PCMan FTP Server. When processing DELETE commands, the server fails to properly validate the length of user-supplied input before copying it into a fixed-size buffer. This allows an attacker to send specially crafted FTP DELETE commands with overly long arguments that overflow the buffer boundaries.

The buffer overflow condition (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer) can corrupt adjacent memory locations, potentially allowing attackers to overwrite critical program data, return addresses, or function pointers. Given the network-accessible nature of FTP servers and the lack of authentication requirements for this attack, this vulnerability presents a significant risk to exposed systems.

Root Cause

The root cause of this vulnerability is improper boundary checking in the DELETE Command Handler. The affected code does not adequately validate the length of input data before performing memory operations, resulting in a classic buffer overflow condition. This type of memory corruption vulnerability typically occurs when fixed-size buffers are used without proper bounds checking, allowing input that exceeds the buffer capacity to overwrite adjacent memory.

Attack Vector

The attack can be initiated remotely over the network against the FTP service, typically running on port 21. An attacker does not require prior authentication to exploit this vulnerability, making it accessible to any network-connected adversary who can reach the FTP server. The attack involves sending a maliciously crafted DELETE command with an oversized argument designed to overflow the target buffer.

The exploitation process involves:

1. Establishing a connection to the vulnerable FTP server
2. Sending a specially crafted DELETE command with an excessively long filename or path argument
3. The overflow corrupts memory, potentially allowing code execution or causing service disruption

The exploit details have been publicly disclosed. Technical details can be found in the Fitoxs Exploit Document and additional information is available via VulDB.

Detection Methods for CVE-2025-3371

Indicators of Compromise

• Anomalous FTP DELETE commands with unusually long arguments (exceeding normal path length limits)
• FTP server crashes or unexpected service restarts
• Abnormal memory consumption patterns in the FTP server process
• Suspicious network connections to port 21 followed by service instability

Detection Strategies

• Monitor FTP traffic for DELETE commands with arguments exceeding 256 characters
• Implement intrusion detection rules to flag oversized FTP command arguments
• Deploy network-based anomaly detection to identify exploitation attempts against FTP services
• Use endpoint detection and response (EDR) solutions to monitor for buffer overflow exploitation patterns

Monitoring Recommendations

• Enable detailed logging for the PCMan FTP Server to capture all command activity
• Configure alerts for FTP service crashes or unexpected restarts
• Monitor network traffic for suspicious patterns targeting port 21
• Implement file integrity monitoring on the FTP server binary and configuration files

How to Mitigate CVE-2025-3371

Immediate Actions Required

• Restrict network access to the FTP server to trusted IP addresses only using firewall rules
• Consider temporarily disabling the FTP service if not critical to operations
• Implement network segmentation to isolate the FTP server from critical infrastructure
• Monitor for exploitation attempts using the detection strategies outlined above

Patch Information

No vendor patch information is currently available for this vulnerability. Organizations should monitor vendor communications and security advisories for updates. In the absence of an official patch, implement the workarounds and mitigations described below to reduce exposure.

Additional vulnerability information can be found at VulDB CTI ID #303617.

Workarounds

• Deploy a Web Application Firewall (WAF) or network-based IPS with rules to filter oversized FTP commands
• Use SFTP or FTPS alternatives that may not be affected by this specific vulnerability
• Implement strict access controls limiting who can connect to the FTP service
• Consider migrating to an alternative FTP server solution until a patch is available

# Firewall rule example to restrict FTP access (Linux iptables)
# Allow FTP only from trusted network range
iptables -A INPUT -p tcp --dport 21 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 21 -j DROP