CVE-2021-40408
📋 TL;DR
This CVE describes an OS command injection vulnerability in Reolink RLC-410W cameras where the DDNS username parameter is not properly validated. Attackers can execute arbitrary commands on the device with root privileges. This affects Reolink RLC-410W v3.0.0.136_20121102 cameras exposed to network access.
💻 Affected Systems
- Reolink RLC-410W
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attackers to install persistent backdoors, pivot to internal networks, or use the device for botnet activities.
Likely Case
Remote code execution leading to camera control takeover, credential theft, or denial of service.
If Mitigated
Limited impact if devices are behind firewalls with strict inbound filtering and no external access.
🎯 Exploit Status
Exploitation requires network access to the device's web interface/API. The vulnerability is well-documented in public advisories.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check with Reolink for latest firmware updates
Vendor Advisory: https://reolink.com/security/
Restart Required: Yes
Instructions:
1. Log into camera web interface. 2. Navigate to System > Maintenance. 3. Check for firmware updates. 4. Download and install latest firmware. 5. Reboot camera after update.
🔧 Temporary Workarounds
Disable DDNS functionality
allTurn off DDNS settings to prevent exploitation via vulnerable endpoint
Network segmentation
allIsolate cameras on separate VLAN with strict firewall rules
🧯 If You Can't Patch
- Block external access to camera web interface (ports 80/443) at network perimeter
- Implement strict inbound firewall rules allowing only trusted IPs to access camera management interface
🔍 How to Verify
Check if Vulnerable:
Check firmware version in camera web interface under System > Device InformationCheck Version:
Check via web interface or use curl to query device info endpointVerify Fix Applied:
Verify firmware version is newer than v3.0.0.136_20121102 and test DDNS functionality📡 Detection & Monitoring
Log Indicators:
- Unusual command execution patterns in system logs
- Multiple failed DDNS configuration attempts
- Suspicious processes spawned from web service
Network Indicators:
- Unusual outbound connections from camera
- Traffic to unexpected ports from camera
- HTTP requests with shell metacharacters in parameters
SIEM Query:
source="camera_logs" AND (command_injection OR shell_metacharacters OR "SetDdns" AND suspicious_payload)