CVE-2021-20991
📋 TL;DR
This vulnerability allows authenticated users on Fibaro Home Center 2 and Lite devices to execute arbitrary commands as the root user through command injection. Attackers can gain complete control of affected devices, potentially compromising home automation systems. Users with firmware version 4.540 or older are affected.
💻 Affected Systems
- Fibaro Home Center 2
- Fibaro Home Center Lite
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device takeover allowing attackers to install persistent malware, pivot to other network devices, steal sensitive data, or disable security systems.
Likely Case
Attackers gain root access to manipulate home automation devices, potentially controlling lights, locks, cameras, and other IoT devices.
If Mitigated
With proper network segmentation and authentication controls, impact is limited to the specific compromised device.
🎯 Exploit Status
Exploit details and proof-of-concept code are publicly available. Requires authenticated access but exploitation is straightforward once credentials are obtained.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firmware version newer than 4.540
Vendor Advisory: https://www.fibaro.com/en/support/
Restart Required: Yes
Instructions:
1. Log into Fibaro Home Center web interface. 2. Navigate to Settings > System > Update. 3. Check for and install available firmware updates. 4. Reboot the device after update completes.
🔧 Temporary Workarounds
Network Segmentation
allIsolate Fibaro devices on separate VLAN or network segment to limit lateral movement.
Access Restriction
linuxRestrict web interface access to trusted IP addresses only using firewall rules.
iptables -A INPUT -p tcp --dport 80 -s TRUSTED_IP -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s TRUSTED_IP -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP
🧯 If You Can't Patch
- Change all device passwords to strong, unique credentials
- Disable remote access and only allow local network connections
🔍 How to Verify
Check if Vulnerable:
Check firmware version in web interface: Settings > System > Information. If version is 4.540 or lower, device is vulnerable.Check Version:
curl -k https://DEVICE_IP/api/settings/system | grep versionVerify Fix Applied:
After update, verify firmware version is higher than 4.540 in Settings > System > Information.📡 Detection & Monitoring
Log Indicators:
- Unusual command execution in system logs
- Multiple failed authentication attempts followed by successful login
- Suspicious processes running as root
Network Indicators:
- Unusual outbound connections from Fibaro device
- Traffic to known malicious IPs
- Unexpected SSH or reverse shell connections
SIEM Query:
source="fibaro_logs" AND (event="command_execution" OR user="root")🔗 References
- http://packetstormsecurity.com/files/162243/Fibaro-Home-Center-MITM-Missing-Authentication-Code-Execution.html
- http://seclists.org/fulldisclosure/2021/Apr/27
- https://www.iot-inspector.com/blog/advisory-fibaro-home-center/
- http://packetstormsecurity.com/files/162243/Fibaro-Home-Center-MITM-Missing-Authentication-Code-Execution.html
- http://seclists.org/fulldisclosure/2021/Apr/27
- https://www.iot-inspector.com/blog/advisory-fibaro-home-center/
