CVE-2010-4816
📋 TL;DR
A null pointer dereference vulnerability in the FTP daemon (ftpd) of affected FreeBSD and OpenBSD systems allows remote attackers to crash the ftpd service, causing denial of service. This affects systems running vulnerable versions of FreeBSD (4.9, 6.3, 8.0) and OpenBSD 4.6 with ftpd enabled. The vulnerability is triggered through specific FTP commands that cause the service to dereference a null pointer.
💻 Affected Systems
- FreeBSD ftpd
- OpenBSD ftpd
📦 What is this software?
Openbsd by Openbsd
Openbsd by Openbsd
Openbsd by Openbsd
Openbsd by Openbsd
⚠️ Risk & Real-World Impact
Worst Case
Remote unauthenticated attacker crashes ftpd service, causing complete denial of FTP service until manual restart. Repeated attacks could create service availability issues.
Likely Case
Remote attacker causes temporary FTP service disruption. Service requires manual restart to recover functionality.
If Mitigated
Minimal impact if ftpd is disabled or properly firewalled. Service disruption limited to FTP only.
🎯 Exploit Status
Proof of concept code was published in security mailing lists. Exploitation requires sending specific FTP commands to trigger the null pointer dereference.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: FreeBSD: patched in subsequent releases; OpenBSD: patched in later versions
Vendor Advisory: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=144761
Restart Required: Yes
Instructions:
1. Update FreeBSD to version 8.1 or later, or apply security patches for affected versions. 2. Update OpenBSD to version 4.7 or later. 3. Restart ftpd service after patching.
🔧 Temporary Workarounds
Disable FTP service
allCompletely disable ftpd if not required
service ftpd stop
chkconfig ftpd off
sysrc ftpd_enable="NO"
Restrict FTP access with firewall
linuxLimit FTP access to trusted networks only
iptables -A INPUT -p tcp --dport 21 -s TRUSTED_NET -j ACCEPT
iptables -A INPUT -p tcp --dport 21 -j DROP
🧯 If You Can't Patch
- Implement network segmentation to isolate FTP servers from untrusted networks
- Use application layer gateway or FTP proxy with protocol validation
🔍 How to Verify
Check if Vulnerable:
Check OS version: uname -a. Check if ftpd is running: ps aux | grep ftpd or service ftpd statusCheck Version:
uname -aVerify Fix Applied:
Verify OS version is patched: uname -a should show version newer than affected versions. Test FTP service functionality.📡 Detection & Monitoring
Log Indicators:
- Multiple ftpd crash/restart events in system logs
- FTP connection attempts followed by service termination
Network Indicators:
- Multiple FTP connections from single source causing service disruption
- Unusual FTP command sequences
SIEM Query:
source="system_logs" AND process="ftpd" AND (event="crash" OR event="segfault")