Overview

A critical vulnerability, designated as CVE-2025-3683, has been discovered in PCMan FTP Server 2.0.7. This vulnerability, which resides within the SIZE Command Handler of the software, can lead to buffer overflow. It is of utmost concern as it allows remote attackers to potentially compromise the system and leak sensitive data, affecting businesses and individuals who utilize PCMan FTP Server 2.0.7.

Vulnerability Summary

CVE ID: CVE-2025-3683
Severity: Critical (CVSS: 7.3)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Potential system compromise and data leakage

Affected Products

Product | Affected Versions

PCMan FTP Server | 2.0.7

How the Exploit Works

The vulnerability lies within the SIZE Command Handler of the PCMan FTP Server 2.0.7. The erroneous handling of the SIZE command can lead to a buffer overflow condition. An attacker can exploit this vulnerability by sending a specially crafted SIZE command that exceeds the buffer limit, causing an overflow. This overflow can then be leveraged to execute arbitrary code, leading to a potential system compromise.

Conceptual Example Code

Below is a conceptual example of how an attacker might exploit this vulnerability. The attacker sends a maliciously crafted SIZE command that exceeds the buffer limit.

POST /SIZE HTTP/1.1
Host: target.example.com
Content-Type: application/json
{ "command": "SIZE", "parameter": "A"*8000 }

In the above example, “A”*8000 represents an excessively long string that causes a buffer overflow.

Mitigation

Users of PCMan FTP Server 2.0.7 are urged to apply the patch provided by the vendor as soon as possible. As a temporary mitigation measure, users could also employ a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) to detect and block attempts to exploit this vulnerability. However, these are merely temporary fixes and do not resolve the underlying issue. Updating to the latest version remains the most effective solution.