CVE-2021-22737
📋 TL;DR
This vulnerability in Schneider Electric homeLYnk and spaceLYnk systems allows attackers to discover credentials through brute force attacks, leading to unauthorized access. It affects homeLYnk (Wiser For KNX) and spaceLYnk products running version 2.60 or earlier. Attackers can gain control of building automation systems.
💻 Affected Systems
- homeLYnk (Wiser For KNX)
- spaceLYnk
📦 What is this software?
Homelynk Firmware by Schneider Electric
Spacelynk Firmware by Schneider Electric
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of building automation system allowing attackers to control lighting, HVAC, security systems, and potentially pivot to other network segments.
Likely Case
Unauthorized access to building management interface leading to manipulation of environmental controls, access logs, and system settings.
If Mitigated
Limited impact with proper network segmentation, strong authentication controls, and monitoring for brute force attempts.
🎯 Exploit Status
Brute force attacks are well-understood and tools for credential brute forcing are widely available. No authentication required to attempt credential discovery.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions after V2.60
Vendor Advisory: https://download.schneider-electric.com/files?p_Doc_Ref=SEVD-2021-130-04
Restart Required: Yes
Instructions:
1. Download latest firmware from Schneider Electric portal. 2. Backup current configuration. 3. Upload and install new firmware via web interface. 4. Verify installation and restore configuration if needed.
🔧 Temporary Workarounds
Network Segmentation
allIsolate building automation systems from general network and internet access
Rate Limiting
allImplement network-level rate limiting for authentication attempts
🧯 If You Can't Patch
- Implement strict network access controls to limit who can reach the management interface
- Deploy intrusion detection systems to monitor for brute force attempts and alert on suspicious activity
🔍 How to Verify
Check if Vulnerable:
Check firmware version in web interface under System Information or Settings. If version is 2.60 or lower, system is vulnerable.Check Version:
No CLI command available. Check via web interface at http://[device-ip]/system/info or similar path.Verify Fix Applied:
After patching, verify firmware version shows higher than 2.60. Test authentication attempts to confirm rate limiting is working.📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts from single IP
- Successful login after many failures
- Authentication logs showing unusual patterns
Network Indicators:
- High volume of HTTP POST requests to login endpoints
- Traffic patterns suggesting automated credential testing
SIEM Query:
source="building-automation" AND (event_type="authentication_failure" COUNT > 10 WITHIN 5min) OR (event_type="authentication_success" AFTER multiple_failures)