CVE-2023-51713
📋 TL;DR
CVE-2023-51713 is a one-byte out-of-bounds read vulnerability in ProFTPD's make_ftp_cmd function that can cause the FTP daemon to crash. This affects ProFTPD servers running versions before 1.3.8a. The vulnerability occurs due to mishandling of quote and backslash semantics in FTP command processing.
💻 Affected Systems
- ProFTPD
📦 What is this software?
Proftpd by Proftpd
⚠️ Risk & Real-World Impact
Worst Case
Denial of service causing FTP service disruption and potential data loss for active transfers
Likely Case
Service crash requiring manual restart of ProFTPD daemon
If Mitigated
Minimal impact with proper monitoring and automated restart mechanisms
🎯 Exploit Status
The vulnerability is in the FTP command parser and can be triggered by sending specially crafted FTP commands
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.3.8a
Vendor Advisory: https://github.com/proftpd/proftpd/blob/1.3.8/NEWS
Restart Required: Yes
Instructions:
1. Download ProFTPD 1.3.8a or later from official sources. 2. Stop the ProFTPD service. 3. Backup configuration files. 4. Install the new version. 5. Restart the ProFTPD service.
🔧 Temporary Workarounds
Network-based mitigation
linuxBlock or restrict FTP access using firewall rules
iptables -A INPUT -p tcp --dport 21 -j DROP
iptables -A INPUT -p tcp --dport 20 -j DROP
Service monitoring and auto-restart
linuxImplement monitoring and automatic restart for ProFTPD service
systemctl enable proftpd
systemctl start proftpd
🧯 If You Can't Patch
- Implement network segmentation to isolate FTP servers from critical systems
- Deploy intrusion detection systems to monitor for exploitation attempts
🔍 How to Verify
Check if Vulnerable:
Check ProFTPD version with: proftpd -vCheck Version:
proftpd -vVerify Fix Applied:
Verify version is 1.3.8a or later: proftpd -v | grep -q '1.3.8a' && echo 'Patched'📡 Detection & Monitoring
Log Indicators:
- ProFTPD daemon crashes
- Segmentation fault errors in system logs
- Unexpected service restarts
Network Indicators:
- Multiple FTP connections with malformed commands
- FTP service becoming unresponsive
SIEM Query:
source="proftpd.log" AND ("segmentation fault" OR "crash" OR "abnormal termination")🔗 References
- https://github.com/proftpd/proftpd/blob/1.3.8/NEWS
- https://github.com/proftpd/proftpd/issues/1683
- https://github.com/proftpd/proftpd/issues/1683#issuecomment-1712887554
- https://github.com/proftpd/proftpd/blob/1.3.8/NEWS
- https://github.com/proftpd/proftpd/issues/1683
- https://github.com/proftpd/proftpd/issues/1683#issuecomment-1712887554
- https://lists.debian.org/debian-lts-announce/2024/11/msg00032.html
