CVE-2025-5596: FreeFloat FTP Server Buffer Overflow Flaw

CVE-2025-5596 Overview

A critical buffer overflow vulnerability has been identified in FreeFloat FTP Server 1.0 affecting the REGET Command Handler component. This vulnerability allows remote attackers to trigger a buffer overflow condition by sending malicious input to the FTP server, potentially leading to arbitrary code execution or system compromise. The exploit has been publicly disclosed and may already be in use by threat actors.

Critical Impact

Remote attackers can exploit the REGET command handler to trigger a buffer overflow, potentially achieving code execution on vulnerable FreeFloat FTP Server installations without authentication.

Affected Products

• FreeFloat FTP Server 1.0
• FreeFloat FTP Server (all installations using version 1.0)

Discovery Timeline

• 2025-06-04 - CVE-2025-5596 published to NVD
• 2025-06-24 - Last updated in NVD database

Technical Details for CVE-2025-5596

Vulnerability Analysis

This vulnerability resides in the REGET command handler of FreeFloat FTP Server 1.0. The REGET command is used in FTP to resume file transfers from a specified offset. The handler fails to properly validate the length of user-supplied input before copying it into a fixed-size buffer, creating a classic buffer overflow condition classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer).

The attack can be launched remotely over the network without requiring any authentication or user interaction. When exploited, this vulnerability allows an attacker to overwrite adjacent memory regions, potentially corrupting program control flow structures such as return addresses or function pointers. This can lead to arbitrary code execution within the context of the FTP server process.

Root Cause

The root cause of this vulnerability is improper bounds checking in the REGET command handler. When processing the REGET command arguments, the server fails to validate the length of the input string before copying it into a stack or heap buffer. This allows an attacker to supply an oversized argument that exceeds the allocated buffer space, resulting in memory corruption.

The vulnerability is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), indicating that the application does not properly restrict write operations to stay within allocated memory boundaries.

Attack Vector

The attack vector for this vulnerability is network-based. An attacker can exploit the vulnerability by:

1. Establishing a connection to the vulnerable FTP server on the default FTP port (typically port 21)
2. Sending a crafted REGET command with an excessively long argument
3. The malformed input overflows the buffer in the REGET command handler
4. Memory corruption occurs, potentially allowing the attacker to redirect execution flow

The vulnerability can be triggered remotely without requiring authentication, making it particularly dangerous for any FreeFloat FTP Server installations exposed to untrusted networks. Technical details and exploit code have been publicly disclosed through Fitoxs Exploit Code.

Detection Methods for CVE-2025-5596

Indicators of Compromise

• Unusual FTP traffic containing abnormally long REGET command arguments
• FTP server crashes or unexpected service terminations
• Evidence of memory corruption or buffer overflow exploitation in process memory
• Network connections to FTP services from suspicious IP addresses followed by malformed commands

Detection Strategies

• Monitor FTP server logs for malformed REGET commands or unusually long command arguments
• Deploy network intrusion detection signatures to identify buffer overflow attempts targeting FTP REGET commands
• Implement application-level monitoring to detect crashes or abnormal behavior in the FreeFloat FTP Server process
• Use memory protection mechanisms such as DEP/ASLR to detect and prevent exploitation attempts

Monitoring Recommendations

• Enable detailed logging on FTP servers to capture all command inputs
• Monitor for repeated connection attempts followed by service crashes, which may indicate exploitation attempts
• Implement network segmentation to isolate FTP services and monitor traffic between segments
• Deploy endpoint detection and response (EDR) solutions to identify post-exploitation activity

How to Mitigate CVE-2025-5596

Immediate Actions Required

• Disable or remove FreeFloat FTP Server 1.0 from production environments immediately
• Restrict network access to the FTP server using firewall rules to limit exposure
• Consider migrating to an actively maintained and secure FTP server alternative
• Monitor existing deployments for signs of exploitation while remediation is in progress

Patch Information

No official patch information is currently available from the vendor for this vulnerability. FreeFloat FTP Server 1.0 is legacy software that may no longer be actively maintained. Organizations should consider replacing FreeFloat FTP Server with a supported FTP server solution that receives regular security updates. For additional vulnerability tracking information, refer to VulDB #311082.

Workarounds

• Implement network-level access controls to restrict FTP server access to trusted IP addresses only
• Deploy a web application firewall (WAF) or network IPS to filter malicious FTP commands
• Consider using SFTP or FTPS alternatives that provide encrypted communications and may offer better security
• If the FTP server must remain operational, run it in an isolated network segment with strict egress filtering

# Example firewall rule to restrict FTP access (iptables)
# Allow FTP 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