CVE-2025-3379: Pcman FTP Server Buffer Overflow Flaw

CVE-2025-3379 Overview

A critical buffer overflow vulnerability has been identified in PCMan FTP Server 2.0.7 affecting the EPSV Command Handler component. This vulnerability allows remote attackers to exploit improper memory operations by sending specially crafted EPSV commands to the server. The manipulation of this command leads to a buffer overflow condition that could enable attackers to corrupt memory, potentially allowing for denial of service or arbitrary code execution.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability in PCMan FTP Server without authentication, potentially compromising server integrity and availability.

Affected Products

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

Discovery Timeline

• 2025-04-07 - CVE-2025-3379 published to NVD
• 2025-04-29 - Last updated in NVD database

Technical Details for CVE-2025-3379

Vulnerability Analysis

This vulnerability resides in the EPSV (Extended Passive Mode) Command Handler of PCMan FTP Server. The EPSV command is part of the FTP protocol extension defined in RFC 2428, which is used to establish data connections in IPv6 environments. The vulnerability arises from improper bounds checking when processing EPSV command input, classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer).

When the FTP server receives a malformed or oversized EPSV command, it fails to properly validate the input length before copying data into a fixed-size buffer. This allows an attacker to overwrite adjacent memory regions, potentially corrupting stack frames, control flow data, or other critical memory structures.

The attack can be launched remotely over the network without requiring any authentication or user interaction, making it particularly dangerous for exposed FTP servers. An exploit for this vulnerability has been disclosed publicly, increasing the risk of active exploitation.

Root Cause

The root cause of CVE-2025-3379 is insufficient bounds checking in the EPSV command parsing routine. The PCMan FTP Server fails to validate the size of incoming EPSV command parameters before processing them, allowing attackers to supply oversized input that exceeds the allocated buffer space. This is a classic buffer overflow condition resulting from unsafe string handling practices common in legacy FTP server implementations.

Attack Vector

The attack vector is network-based, requiring no prior authentication or privileges. An attacker can connect to the vulnerable FTP server on the standard FTP port and issue a malformed EPSV command containing excessive or specially crafted data. The server processes this command without proper validation, triggering the buffer overflow.

The vulnerability manifests in the EPSV command handler when parsing client-supplied input. For technical details regarding the exploitation mechanism, refer to the Fitoxs Exploit Document and the VulDB Entry #303625 for additional analysis.

Detection Methods for CVE-2025-3379

Indicators of Compromise

• Unusual or malformed EPSV commands in FTP server logs with excessive parameter lengths
• FTP server crashes or unexpected restarts coinciding with network connections
• Memory access violations or segmentation faults in PCMan FTP Server process logs
• Network traffic containing oversized FTP EPSV command payloads targeting port 21

Detection Strategies

• Deploy network intrusion detection signatures to identify abnormally long EPSV command sequences
• Monitor FTP server process stability and investigate unexpected terminations
• Implement log analysis rules to flag EPSV commands exceeding normal parameter lengths
• Configure SentinelOne endpoint protection to detect buffer overflow exploitation attempts on FTP server processes

Monitoring Recommendations

• Enable verbose FTP logging to capture full command sequences from client connections
• Set up alerts for PCMan FTP Server process crashes or memory violations
• Monitor network traffic to FTP servers for unusual connection patterns or payload sizes
• Implement real-time file integrity monitoring on FTP server binaries and configurations

How to Mitigate CVE-2025-3379

Immediate Actions Required

• Discontinue use of PCMan FTP Server 2.0.7 and migrate to a supported, actively maintained FTP server solution
• Restrict network access to the FTP server using firewall rules to limit exposure
• Implement network segmentation to isolate FTP services from critical infrastructure
• Deploy intrusion prevention systems capable of filtering malformed FTP commands

Patch Information

No vendor patch is currently available for this vulnerability. PCMan FTP Server appears to be abandoned software without active maintenance or security updates. Organizations are strongly advised to migrate to alternative FTP server solutions that receive regular security updates.

For reference, technical details are available through the VulDB CTI Report #303625.

Workarounds

• Replace PCMan FTP Server with actively maintained alternatives such as FileZilla Server, vsftpd, or ProFTPD
• Implement network-level filtering to block EPSV commands if extended passive mode is not required
• Use a reverse proxy or application firewall to validate and sanitize FTP command parameters
• Restrict FTP server access to trusted IP addresses only via firewall rules

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

# Alternative: Disable the service entirely if not required
net stop "PCMan FTP Server"
sc config "PCMan FTP Server" start=disabled