CVE-2021-42624
📋 TL;DR
This is a local buffer overflow vulnerability in Miniftpd's ftpproto.c file that allows attackers to execute arbitrary code or crash the service by sending a crafted payload. It affects systems running vulnerable versions of Miniftpd FTP server software. Attackers need access to the FTP service to exploit this vulnerability.
💻 Affected Systems
- Miniftpd
📦 What is this software?
Miniftpd by Miniftpd Project
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or installation of persistent malware.
Likely Case
Service disruption through denial of service (crash) or limited code execution within the FTP service context.
If Mitigated
Minimal impact if proper network segmentation and least privilege principles are applied to FTP service accounts.
🎯 Exploit Status
Exploitation requires FTP access but buffer overflow vulnerabilities in network services are commonly weaponized. The GitHub issue shows proof-of-concept details.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check GitHub repository for fixed version
Vendor Advisory: https://github.com/Gabe-commiter/Miniftpd/issues/4
Restart Required: Yes
Instructions:
1. Check Miniftpd GitHub repository for patched version. 2. Download and compile the fixed version. 3. Stop the Miniftpd service. 4. Replace the binary with the patched version. 5. Restart the Miniftpd service.
🔧 Temporary Workarounds
Network Access Restriction
linuxRestrict FTP access to trusted IP addresses only using firewall rules
iptables -A INPUT -p tcp --dport 21 -s TRUSTED_IP -j ACCEPT
iptables -A INPUT -p tcp --dport 21 -j DROP
Service Account Hardening
linuxRun Miniftpd under a restricted service account with minimal privileges
useradd -r -s /bin/false miniftpd_user
chown -R miniftpd_user:miniftpd_user /path/to/miniftpd
🧯 If You Can't Patch
- Replace Miniftpd with alternative FTP server software like vsftpd or proftpd
- Disable FTP service entirely and use secure alternatives like SFTP or FTPS
🔍 How to Verify
Check if Vulnerable:
Check if Miniftpd is running and compare version against GitHub repository for known vulnerable versionsCheck Version:
miniftpd --version or check compilation date/source code versionVerify Fix Applied:
Verify the patched version is installed and test with proof-of-concept payload from GitHub issue📡 Detection & Monitoring
Log Indicators:
- Unusual FTP command sequences
- Service crashes/restarts
- Large or malformed FTP commands
Network Indicators:
- Crafted FTP commands triggering buffer overflow patterns
- Multiple connection attempts with payload variations
SIEM Query:
source="ftp.log" AND (command_size>threshold OR command="*crafted*" OR process="miniftpd" AND event="crash")