CVE-2025-5051: FreeFloat FTP Server Buffer Overflow Flaw

CVE-2025-5051 Overview

A critical buffer overflow vulnerability has been identified in FreeFloat FTP Server 1.0. The vulnerability exists within the BINARY Command Handler component, where improper input validation allows attackers to trigger a buffer overflow condition. This flaw can be exploited remotely over the network without requiring authentication, potentially enabling attackers to corrupt memory, crash the service, or achieve code execution on vulnerable systems.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability in FreeFloat FTP Server's BINARY command handling to compromise system integrity, confidentiality, and availability without authentication.

Affected Products

• FreeFloat FTP Server 1.0
• Systems running FreeFloat FTP Server with the BINARY command enabled
• Network-accessible FTP deployments using vulnerable FreeFloat versions

Discovery Timeline

• May 21, 2025 - CVE-2025-5051 published to NVD
• June 23, 2025 - Last updated in NVD database

Technical Details for CVE-2025-5051

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), indicating that the BINARY Command Handler fails to properly validate input boundaries before processing user-supplied data. The flaw resides in how the FTP server processes the BINARY command, which is used to set the file transfer mode. When an attacker sends a maliciously crafted BINARY command with excessive or specially formatted input, the server fails to enforce proper bounds checking, resulting in memory corruption.

The attack can be launched remotely over the network without requiring any prior authentication or user interaction. This makes the vulnerability particularly dangerous in internet-facing FTP deployments. The exploit has been publicly disclosed, increasing the risk of active exploitation in the wild.

Root Cause

The root cause of this vulnerability stems from insufficient input validation in the BINARY Command Handler component of FreeFloat FTP Server. The affected function does not properly verify the length or format of user-supplied data before copying it into a fixed-size memory buffer. This classic buffer overflow condition allows attackers to write beyond the allocated memory boundaries, potentially overwriting adjacent memory structures, return addresses, or function pointers.

Attack Vector

The attack vector for CVE-2025-5051 is network-based, allowing remote exploitation. An attacker can connect to a vulnerable FreeFloat FTP Server instance and send a specially crafted BINARY command containing oversized or malformed input data. The attack requires no authentication credentials and no user interaction, making it highly accessible to potential threat actors.

The exploitation process involves establishing a connection to the FTP server on the default port (typically 21), then sending a BINARY command with a payload designed to overflow the vulnerable buffer. Depending on the exploitation technique employed, this could lead to denial of service through application crashes, or potentially arbitrary code execution if the attacker can precisely control the overwritten memory contents.

Technical details and exploit information have been documented in external references including the Fitoxs Exploit Document and VulDB entry #309870.

Detection Methods for CVE-2025-5051

Indicators of Compromise

• Unusual FTP traffic patterns with abnormally long BINARY command strings
• FTP server crashes or unexpected service restarts
• Memory access violations in FreeFloat FTP Server process logs
• Network connections to FTP services followed by service termination

Detection Strategies

• Monitor FTP command logs for BINARY commands with unusually long parameter strings exceeding normal operational thresholds
• Implement network intrusion detection rules to identify buffer overflow attack patterns targeting FTP services
• Deploy application-level monitoring to detect memory corruption attempts or abnormal process behavior in FTP server instances
• Use SentinelOne's behavioral AI to identify exploitation attempts through anomalous process activity

Monitoring Recommendations

• Enable detailed FTP command logging to capture all BINARY command invocations and their parameters
• Configure alerting for FTP service crashes or unexpected restarts that may indicate exploitation attempts
• Monitor network traffic for reconnaissance activity targeting FTP services on port 21
• Implement file integrity monitoring on FTP server binaries to detect potential post-exploitation modifications

How to Mitigate CVE-2025-5051

Immediate Actions Required

• Restrict network access to FreeFloat FTP Server instances using firewall rules to limit exposure
• Disable or block external access to the FTP service until patching can be completed
• Consider migrating to a more actively maintained FTP server solution with regular security updates
• Implement network segmentation to isolate FTP servers from critical internal resources

Patch Information

As of the last NVD update, no official vendor patch has been released for this vulnerability. FreeFloat FTP Server 1.0 is legacy software that may no longer receive security updates. Organizations should evaluate alternative FTP server solutions that are actively maintained and receive regular security patches. Refer to VulDB submission #581283 for the latest information on this vulnerability.

Workarounds

• Place vulnerable FTP servers behind a reverse proxy or application firewall that can filter malicious BINARY commands
• Implement strict access control lists (ACLs) to limit FTP access to trusted IP addresses only
• Consider using VPN-only access for FTP services to reduce the attack surface
• Deploy SentinelOne endpoint protection to detect and block exploitation attempts at the endpoint level

# Firewall configuration to restrict FTP access (example using iptables)
# Restrict FTP access to trusted networks only
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 FTP service entirely if not required
systemctl stop freefloat-ftp
systemctl disable freefloat-ftp