CVE-2020-21937
📋 TL;DR
This CVE describes a command injection vulnerability in the HNAP1/SetWLanApcliSettings endpoint of Motorola CX2 routers. Attackers can execute arbitrary system commands on affected devices, potentially taking full control. Users of Motorola CX2 routers with the vulnerable firmware are affected.
💻 Affected Systems
- Motorola CX2 router
📦 What is this software?
Cx2 Firmware by Motorola
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the router allowing attackers to intercept all network traffic, install persistent malware, pivot to internal networks, and use the device for botnet activities.
Likely Case
Router takeover leading to DNS hijacking, credential theft from network traffic, and use as a foothold for attacking other devices on the local network.
If Mitigated
Limited impact if the router is behind a firewall with restricted WAN access and proper network segmentation is in place.
🎯 Exploit Status
The exploit requires network access to the router's web interface/HNAP endpoint. Public proof-of-concept code exists in GitHub repositories.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: No known vendor advisory
Restart Required: No
Instructions:
No official patch available. Check Motorola/Arris website for firmware updates. If available, download and install through router admin interface.
🔧 Temporary Workarounds
Disable HNAP1 protocol
allDisable the HNAP1 protocol if not required for functionality
Restrict WAN access
allConfigure firewall to block external access to router admin interface (typically ports 80, 443, 8080)
🧯 If You Can't Patch
- Replace affected routers with supported models
- Isolate routers in separate VLAN with strict access controls
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface. If version matches affected version, device is vulnerable.Check Version:
Check router web interface at http://[router-ip]/ or use nmap to identify device model and firmwareVerify Fix Applied:
Verify firmware has been updated to a version newer than the affected build.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /HNAP1/SetWLanApcliSettings with shell metacharacters
- Unexpected system command execution in router logs
Network Indicators:
- Unusual outbound connections from router
- DNS queries to suspicious domains from router
SIEM Query:
source="router_logs" AND uri="/HNAP1/SetWLanApcliSettings" AND (request CONTAINS "|" OR request CONTAINS ";" OR request CONTAINS "`" OR request CONTAINS "$")