CVE-2020-6162
📋 TL;DR
CVE-2020-6162 is an out-of-bounds read vulnerability in Bftpd FTP server that causes the daemon to crash during startup under certain conditions. This affects Bftpd 5.3 installations where the hidegroups_init function fails due to uninitialized values. The vulnerability prevents the FTP service from starting, resulting in denial of service.
💻 Affected Systems
- Bftpd FTP Server
📦 What is this software?
Bftpd by Bftpd Project
⚠️ Risk & Real-World Impact
Worst Case
Complete denial of service preventing FTP server startup and availability, potentially requiring manual intervention to restore service.
Likely Case
FTP server fails to start, causing service disruption until patched or workaround applied.
If Mitigated
Minimal impact if server is already running stable version or if workarounds prevent the triggering condition.
🎯 Exploit Status
Exploitation requires ability to influence server configuration or trigger the specific condition during startup.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Bftpd 5.4 and later
Vendor Advisory: http://bftpd.sourceforge.net/news.html
Restart Required: Yes
Instructions:
1. Download Bftpd 5.4 or later from official source. 2. Stop Bftpd service. 3. Install new version following distribution package manager or source compilation. 4. Restart Bftpd service.
🔧 Temporary Workarounds
Avoid hidegroups configuration
linuxPrevent triggering the vulnerable code path by not using hidegroups feature
# Edit bftpd.conf and remove or comment hidegroups lines
# systemctl restart bftpd
Downgrade to stable version
linuxRevert to Bftpd 5.2 or earlier stable version
# apt-get install bftpd=5.2* (Debian/Ubuntu)
# yum downgrade bftpd-5.2* (RHEL/CentOS)
🧯 If You Can't Patch
- Monitor Bftpd service status and restart if crashes occur
- Implement external monitoring to detect FTP service downtime
🔍 How to Verify
Check if Vulnerable:
Check Bftpd version: bftpd -v or check installed package version. If version is exactly 5.3, system is vulnerable.Check Version:
bftpd -v 2>&1 | grep -i version || dpkg -l | grep bftpd || rpm -qa | grep bftpdVerify Fix Applied:
Verify Bftpd version is 5.4 or later and service starts successfully without hidegroups_init errors.📡 Detection & Monitoring
Log Indicators:
- Segmentation fault or crash messages in system logs during Bftpd startup
- Error messages containing 'hidegroups_init' or 'dirlist.c'
Network Indicators:
- FTP service unavailable on port 21
- Failed connection attempts to FTP port
SIEM Query:
source="systemd" AND "bftpd" AND ("segmentation fault" OR "crash" OR "failed")