CVE-2021-20122
📋 TL;DR
This vulnerability allows authenticated attackers on the Telus Wi-Fi Hub's local network to execute arbitrary commands with root privileges. Attackers need either super user credentials or can combine it with authentication bypass vulnerabilities like CVE-2021-20090. This affects Telus Wi-Fi Hub PRV65B444A-S-TS devices with vulnerable firmware.
💻 Affected Systems
- Telus Wi-Fi Hub PRV65B444A-S-TS
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full device compromise with root shell access, allowing attackers to intercept all network traffic, install persistent malware, pivot to other network devices, or use the device for botnet activities.
Likely Case
Local network attackers gaining complete control of the router, enabling traffic monitoring, DNS hijacking, credential theft, and network reconnaissance.
If Mitigated
Limited impact if proper network segmentation isolates the router management interface and strong authentication is enforced.
🎯 Exploit Status
Exploitation requires authentication or combination with CVE-2021-20090 authentication bypass. Command injection is straightforward once authenticated.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firmware version newer than 3.00.20
Vendor Advisory: https://www.tenable.com/security/research/tra-2021-41
Restart Required: Yes
Instructions:
1. Log into Telus Wi-Fi Hub admin interface. 2. Navigate to firmware update section. 3. Check for and apply latest firmware update. 4. Reboot device after update completes.
🔧 Temporary Workarounds
Disable TR-069 Management Interface
allDisable the vulnerable TR-069 interface if not required for device management.
Network Segmentation
allIsolate router management interface to dedicated VLAN with strict access controls.
🧯 If You Can't Patch
- Implement strict network segmentation to isolate router management interface
- Enforce strong authentication policies and monitor for authentication bypass attempts
🔍 How to Verify
Check if Vulnerable:
Check firmware version via admin interface. If version is 3.00.20 and TR-069 interface is enabled, device is vulnerable.Check Version:
Check via web interface: Admin > System > Firmware VersionVerify Fix Applied:
Verify firmware version is newer than 3.00.20 and test command injection attempts fail.📡 Detection & Monitoring
Log Indicators:
- Unusual TR-069 requests
- Multiple authentication attempts
- Suspicious command execution in system logs
Network Indicators:
- Unusual outbound connections from router
- Suspicious traffic patterns from router management interface
SIEM Query:
source="router_logs" AND ("tr69_cmd.cgi" OR "command injection" OR "root shell")