CVE-2024-0548: FreeFloat FTP Server DoS Vulnerability

CVE-2024-0548 Overview

CVE-2024-0548 is a remotely exploitable denial-of-service vulnerability in FreeFloat FTP Server 1.0. The flaw resides in the SIZE command handler, where improper resource handling [CWE-404] allows an attacker to crash the service. An unauthenticated remote attacker can send crafted FTP traffic to terminate the service, disrupting file transfer availability for legitimate users. The vulnerability was published to the National Vulnerability Database (NVD) on January 15, 2024, and is tracked as VulDB identifier VDB-250718. Public exploit details have been released through Packet Storm, increasing the likelihood of opportunistic exploitation against exposed instances.

Critical Impact
An unauthenticated remote attacker can crash the FreeFloat FTP Server through the SIZE command, eliminating availability of file transfer services.

Affected Products

FreeFloat FTP Server 1.0
CPE: cpe:2.3:a:freefloat_ftp_server_project:freefloat_ftp_server:1.0
Component: SIZE Command Handler

Discovery Timeline

2024-01-15 - CVE-2024-0548 published to NVD with public exploit disclosure
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-0548

Vulnerability Analysis

The vulnerability resides in how FreeFloat FTP Server 1.0 processes the FTP SIZE command. The SIZE command, defined in RFC 3659, returns the byte length of a specified file on the server. FreeFloat's implementation fails to safely handle malformed or unexpected input passed to this command. Triggering the flaw results in a service crash that meets the conditions of [CWE-404] Improper Resource Shutdown or Release.

The attack requires no authentication and no user interaction. An attacker reaching the FTP listener over the network can send a crafted SIZE request and terminate the daemon. Because FreeFloat FTP Server is a single-process service without supervised restart, recovery requires manual intervention or external process management.

The Exploit Prediction Scoring System (EPSS) places CVE-2024-0548 at the 67th percentile, indicating measurable real-world exploitation likelihood given the public proof-of-concept on Packet Storm.

Root Cause

The root cause is improper resource handling within the SIZE Command Handler. The handler does not validate or constrain inputs to a safe operational state, allowing a malformed argument to drive the process into an unrecoverable condition. FreeFloat is unmaintained software, and no upstream patch addresses this defect.

Attack Vector

The attack vector is network-based against TCP port 21 (or any configured FTP listener). The attacker establishes an FTP session and issues a crafted SIZE command. Anonymous or authenticated context is not a prerequisite if the server is configured to accept connections from untrusted networks. Public exploitation details are available in the Packet Storm DoS Report and the VulDB entry.

No verified exploitation code is reproduced here. Reviewers should consult the referenced disclosure sources for technical proof-of-concept details.

Detection Methods for CVE-2024-0548

Indicators of Compromise

Unexpected termination of the freefloatftpserver.exe process on hosts running FreeFloat FTP Server 1.0
FTP control channel sessions containing SIZE commands with abnormally long or malformed arguments
Repeated short-lived TCP connections to port 21 from a single external source followed by service unavailability
Event log entries showing application crash dumps tied to the FreeFloat FTP service

Detection Strategies

Inspect FTP control traffic at the network perimeter for SIZE commands with oversized or non-printable arguments
Correlate FTP service crash events with inbound connection logs to identify the source IP triggering the failure
Use process monitoring to alert on unexpected exits of the FreeFloat FTP Server binary
Apply network intrusion detection signatures for FTP command anomalies targeting SIZE handling

Monitoring Recommendations

Enable FTP protocol logging and forward logs to a centralized SIEM for command-level analysis
Track baseline availability of FTP services and alert on repeated restarts within short intervals
Monitor for inbound connections to legacy FTP servers from unexpected geographies or IP reputations
Review firewall and NetFlow data for scanning patterns targeting TCP/21 across the environment

How to Mitigate CVE-2024-0548

Immediate Actions Required

Decommission FreeFloat FTP Server 1.0 and migrate to a maintained FTP or SFTP solution such as vsftpd, ProFTPD, or OpenSSH SFTP
Restrict inbound access to TCP port 21 using firewall allowlists limited to known administrative sources
Disable any internet exposure of FreeFloat FTP Server until replacement is complete
Audit the environment for unmanaged instances of FreeFloat FTP Server using asset discovery tooling

Patch Information

No vendor patch is available for CVE-2024-0548. FreeFloat FTP Server is unmaintained, and the vendor has not issued a fixed release. Replacement of the affected software is the only durable remediation. Reference the VulDB advisory for tracking updates.

Workarounds

Place FreeFloat FTP Server behind an application-aware firewall that drops malformed SIZE commands
Use a reverse FTP proxy that performs strict command validation before forwarding to the backend
Enforce network segmentation so that FTP services are reachable only from internal management networks
Implement process supervision to automatically restart the service after a crash while replacement is in progress

bash

# Example: restrict FTP exposure to a single management subnet using iptables
iptables -A INPUT -p tcp --dport 21 -s 10.10.20.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 21 -j DROP