CVE-2020-37067
📋 TL;DR
CVE-2020-37067 is a critical buffer overflow vulnerability in Filetto 1.0 FTP server that allows unauthenticated attackers to crash the service by sending an oversized FEAT command. This creates a denial of service condition, making the FTP server unavailable to legitimate users. Anyone running Filetto 1.0 FTP server is affected.
💻 Affected Systems
- Filetto FTP Server
⚠️ Risk & Real-World Impact
Worst Case
Complete service disruption of the FTP server, potentially affecting dependent services or business operations that rely on file transfers.
Likely Case
FTP service becomes unresponsive and requires manual restart, causing temporary file transfer interruptions.
If Mitigated
Minimal impact if the service is behind network controls or not internet-facing, though internal attackers could still exploit.
🎯 Exploit Status
Exploit code is publicly available on Exploit-DB (ID 48503) and requires minimal technical skill to execute.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: N/A
Vendor Advisory: N/A
Restart Required: No
Instructions:
No official patch exists. Consider migrating to a maintained FTP server solution or implementing workarounds.
🔧 Temporary Workarounds
Network Filtering
linuxBlock or filter oversized FEAT commands at network perimeter using firewall or IPS rules.
iptables -A INPUT -p tcp --dport 21 -m string --string "FEAT" --algo bm -m length --length 11008 -j DROP
Service Restriction
linuxRestrict FTP server access to trusted IP addresses only.
iptables -A INPUT -p tcp --dport 21 -s trusted_ip_range -j ACCEPT
iptables -A INPUT -p tcp --dport 21 -j DROP
🧯 If You Can't Patch
- Replace Filetto with a maintained, secure FTP server alternative like vsftpd or FileZilla Server.
- Implement network segmentation to isolate the FTP server from untrusted networks.
🔍 How to Verify
Check if Vulnerable:
Check if Filetto 1.0 is installed and running on port 21. Use netstat to identify listening services: netstat -tulpn | grep :21Check Version:
Check application documentation or process information for version details.Verify Fix Applied:
Test with the exploit payload from Exploit-DB 48503. If service remains responsive, workaround may be effective.📡 Detection & Monitoring
Log Indicators:
- FTP service crash logs
- Unusual large FEAT command entries in FTP logs
- Service restart events
Network Indicators:
- Large (11,008+ byte) FTP FEAT commands
- Multiple connection attempts followed by service unavailability
SIEM Query:
source="ftp.log" AND command="FEAT" AND size>11000