CVE-2025-3375: PCMan FTP Server Buffer Overflow Flaw

CVE-2025-3375 Overview

A critical buffer overflow vulnerability has been discovered in PCMan FTP Server version 2.0.7. This vulnerability affects the CDUP Command Handler component, allowing attackers to exploit improper buffer operations. The flaw can be triggered remotely over the network without authentication, making it a significant security risk for any systems running the affected software. The exploit has been publicly disclosed, increasing the urgency for affected organizations to take protective measures.

Critical Impact
Remote attackers can exploit the buffer overflow in the CDUP Command Handler to potentially execute arbitrary code or cause denial of service on vulnerable PCMan FTP Server 2.0.7 installations.

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-2025-3375 published to NVD
May 16, 2025 - Last updated in NVD database

Technical Details for CVE-2025-3375

Vulnerability Analysis

This vulnerability resides in the CDUP Command Handler of PCMan FTP Server 2.0.7. The CDUP command (Change to Parent Directory) is a standard FTP protocol command used to navigate directory structures. When processing CDUP commands, the server fails to properly validate input boundaries, leading to a buffer overflow condition (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer).

The vulnerability can be exploited remotely over the network without requiring any authentication or user interaction. When a malicious CDUP command is crafted with oversized or specially formatted data, it overflows the internal buffer allocated for processing, potentially corrupting adjacent memory regions. This memory corruption can lead to denial of service through application crashes, or potentially enable arbitrary code execution if an attacker can precisely control the overflow data.

Root Cause

The root cause is improper input validation and boundary checking in the CDUP Command Handler. The application does not adequately verify the length or format of data associated with CDUP command processing, allowing data to exceed the allocated buffer size. This is a classic buffer overflow scenario where the developer failed to implement proper bounds checking before copying or processing user-supplied input.

Attack Vector

The attack vector is network-based, allowing remote exploitation. An attacker can connect to the vulnerable FTP server and send a malformed CDUP command to trigger the buffer overflow. The attack requires no authentication and no user interaction, making it highly accessible to potential attackers with network access to the FTP service.

The exploitation process involves:

Establishing a connection to the vulnerable PCMan FTP Server on port 21 (or configured FTP port)
Sending a crafted CDUP command with an oversized payload
The server processes the malformed command without proper bounds checking
Buffer overflow occurs, potentially overwriting critical memory structures

Technical details and a proof-of-concept are available in the Fitoxs Exploit Report.

Detection Methods for CVE-2025-3375

Indicators of Compromise

Unexpected crashes or service restarts of PCMan FTP Server processes
Anomalous network traffic patterns involving large or malformed CDUP commands to the FTP service
Core dumps or memory error logs associated with the FTP server process
Unusual authentication attempts or connection patterns to the FTP service

Detection Strategies

Monitor FTP server logs for abnormal CDUP command sequences or unusually large command payloads
Deploy network intrusion detection systems (IDS) with signatures for buffer overflow attempts targeting FTP services
Implement application-level monitoring to detect unexpected process terminations or memory corruption events
Use endpoint detection and response (EDR) solutions to identify exploitation attempts and post-exploitation behavior

Monitoring Recommendations

Enable verbose logging on FTP servers to capture detailed command sequences
Configure network monitoring to alert on anomalous FTP traffic patterns
Implement file integrity monitoring on FTP server binaries and configuration files
Review server event logs regularly for unexpected service interruptions or crash events

How to Mitigate CVE-2025-3375

Immediate Actions Required

Discontinue use of PCMan FTP Server 2.0.7 if possible and migrate to a more secure, actively maintained FTP server solution
Restrict network access to the FTP server using firewall rules to limit exposure to trusted IP addresses only
Implement network segmentation to isolate FTP servers from critical internal systems
Deploy Web Application Firewalls (WAF) or network security appliances capable of inspecting and filtering FTP traffic

Patch Information

No vendor patch information is currently available for this vulnerability. PCMan FTP Server appears to be legacy software without active maintenance. Organizations should evaluate migration to alternative FTP server solutions that receive regular security updates.

For additional vulnerability intelligence, refer to:

Workarounds

Restrict FTP server access to trusted IP addresses using host-based or network firewall rules
Consider deploying the FTP server behind a reverse proxy or application-level gateway that can filter malformed commands
Disable the FTP service entirely if it is not business-critical
Implement network intrusion prevention systems (IPS) configured to block known buffer overflow attack patterns
Migrate to secure alternatives such as SFTP or FTPS implementations with active vendor support

bash

# Example: Restrict FTP access using iptables (Linux)
# Allow FTP access only from trusted network
iptables -A INPUT -p tcp --dport 21 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 21 -j DROP

# Example: Windows Firewall rule to restrict FTP access
netsh advfirewall firewall add rule name="Restrict FTP" dir=in action=allow protocol=tcp localport=21 remoteip=192.168.1.0/24