CVE-2025-3762: Pcman FTP Server Buffer Overflow Flaw

CVE-2025-3762 Overview

A critical buffer overflow vulnerability has been identified in PCMan FTP Server version 2.0.7. The vulnerability exists within the MPUT Command Handler component, where improper handling of input data leads to a buffer overflow condition. This flaw can be exploited remotely by attackers without requiring authentication, potentially allowing them to crash the service or execute arbitrary code on vulnerable systems.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability in PCMan FTP Server's MPUT Command Handler to cause denial of service or potentially achieve code execution on affected systems.

Affected Products

• PCMan FTP Server 2.0.7
• Systems running vulnerable PCMan FTP Server installations
• Windows-based environments hosting PCMan FTP services

Discovery Timeline

• 2025-04-17 - CVE-2025-3762 published to NVD
• 2025-05-12 - Last updated in NVD database

Technical Details for CVE-2025-3762

Vulnerability Analysis

This vulnerability affects the MPUT Command Handler in PCMan FTP Server 2.0.7. The MPUT command is typically used in FTP clients to upload multiple files to the server. The vulnerable component fails to properly validate the length of user-supplied input before copying it into a fixed-size buffer in memory. This creates a classic buffer overflow condition that can be triggered remotely over the network.

The vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), which encompasses memory corruption issues where operations occur outside intended memory boundaries. When exploited, this can lead to memory corruption, service crashes, or in more severe scenarios, arbitrary code execution if an attacker can control the overwritten memory regions.

The attack requires no prior authentication to the FTP server and can be initiated from any network location that can reach the vulnerable service, making it particularly dangerous for internet-facing FTP servers.

Root Cause

The root cause of this vulnerability is insufficient bounds checking in the MPUT Command Handler. When processing MPUT commands, the handler does not properly validate the size of the input data against the allocated buffer space. This allows an attacker to supply specially crafted input that exceeds the buffer's capacity, causing data to be written beyond the intended memory boundaries.

This is a common programming error in legacy applications written in languages like C/C++ that require manual memory management. The lack of proper input validation combined with the use of unsafe string handling functions creates the conditions necessary for a buffer overflow attack.

Attack Vector

The attack can be launched remotely over the network by connecting to the vulnerable FTP server and sending a maliciously crafted MPUT command. The attacker does not need authentication credentials, as the vulnerability can be triggered before or during the authentication process, or against anonymous FTP access if enabled.

The exploitation process involves:

1. Establishing a connection to the vulnerable PCMan FTP Server on port 21 (or configured FTP port)
2. Sending an oversized or specially crafted MPUT command with excessive data
3. The malformed input overflows the internal buffer, corrupting adjacent memory
4. Depending on the attacker's skill and the system configuration, this can result in denial of service or code execution

Technical details regarding the specific exploit methodology have been publicly disclosed. For more information, see the Fitoxs Exploit Document and VulDB entry #305396.

Detection Methods for CVE-2025-3762

Indicators of Compromise

• Unexpected crashes or restarts of the PCMan FTP Server service
• Large or malformed MPUT commands in FTP server logs
• Network traffic containing oversized FTP command payloads targeting port 21
• Memory access violations or segmentation faults in application crash dumps

Detection Strategies

• Monitor FTP server logs for unusually long MPUT commands or repeated connection attempts followed by service failures
• Implement network intrusion detection rules to identify oversized FTP command payloads
• Deploy endpoint detection and response (EDR) solutions capable of detecting buffer overflow exploitation attempts
• Use application crash monitoring to detect repeated service failures that may indicate exploitation attempts

Monitoring Recommendations

• Enable verbose logging on FTP services to capture full command details
• Configure alerts for FTP service crashes or unexpected restarts
• Monitor network traffic for anomalous patterns targeting FTP services
• Review system event logs for memory-related errors associated with the FTP server process

How to Mitigate CVE-2025-3762

Immediate Actions Required

• Disable or restrict access to PCMan FTP Server if not immediately required
• Implement network segmentation to limit exposure of FTP services to trusted networks only
• Deploy firewall rules to restrict FTP access to known, trusted IP addresses
• Consider migrating to an actively maintained and secure FTP server alternative
• Enable SentinelOne Singularity platform for endpoint protection against exploitation attempts

Patch Information

No official vendor patch information is currently available for this vulnerability. PCMan FTP Server is legacy software that may no longer receive security updates. Organizations using this software should strongly consider migrating to a more secure, actively maintained FTP server solution.

For additional vulnerability details and community tracking, refer to the VulDB CTI entry.

Workarounds

• Replace PCMan FTP Server with a modern, actively maintained FTP server such as FileZilla Server or OpenSSH SFTP
• If replacement is not immediately possible, restrict network access to the FTP server using firewall rules
• Disable anonymous FTP access and enforce strong authentication if the server must remain operational
• Monitor for exploitation attempts using network and host-based intrusion detection systems
• Consider using SentinelOne's Singularity XDR platform to detect and block buffer overflow exploitation in real-time

# Firewall configuration example (Windows)
# Restrict FTP access to trusted IP ranges only
netsh advfirewall firewall add rule name="Block FTP External" dir=in action=block protocol=TCP localport=21
netsh advfirewall firewall add rule name="Allow FTP Trusted" dir=in action=allow protocol=TCP localport=21 remoteip=10.0.0.0/8,192.168.0.0/16