CVE-2021-41383
📋 TL;DR
This vulnerability allows authenticated administrators on NETGEAR R6020 routers to execute arbitrary shell commands by injecting shell metacharacters into the ntp_server field in setup.cgi. This enables remote code execution with administrative privileges. Only users with admin access to affected NETGEAR R6020 routers are impacted.
💻 Affected Systems
- NETGEAR R6020
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
An attacker with admin credentials could gain full control of the router, intercept all network traffic, deploy persistent malware, pivot to internal networks, or brick the device.
Likely Case
An attacker with stolen or default admin credentials executes commands to modify router settings, steal credentials, or deploy crypto-mining malware.
If Mitigated
With strong unique admin passwords and network segmentation, impact is limited to the router itself without lateral movement.
🎯 Exploit Status
Exploit requires admin credentials but is trivial to execute once authenticated.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.0.0.62 or later
Vendor Advisory: https://kb.netgear.com/000064437/Security-Advisory-for-Pre-Authentication-Command-Injection-on-Some-Routers-PSV-2021-0083
Restart Required: Yes
Instructions:
1. Log into router admin interface. 2. Navigate to Advanced > Administration > Firmware Update. 3. Check for updates and install version 1.0.0.62 or later. 4. Reboot router after update.
🔧 Temporary Workarounds
Change Admin Password
allUse a strong unique password for admin access to prevent credential-based attacks.
Disable Remote Management
allPrevent external access to admin interface.
🧯 If You Can't Patch
- Isolate router on separate VLAN with strict firewall rules
- Implement network monitoring for unusual admin login attempts or command execution patterns
🔍 How to Verify
Check if Vulnerable:
Check router firmware version via admin interface at Advanced > Administration > Firmware Update. If version is 1.0.0.48, device is vulnerable.Check Version:
curl -s http://routerlogin.com/currentsetting.htm | grep firmwareVerify Fix Applied:
Confirm firmware version is 1.0.0.62 or later in admin interface.📡 Detection & Monitoring
Log Indicators:
- Unusual admin login attempts
- setup.cgi requests with shell metacharacters in parameters
- Unexpected command execution in system logs
Network Indicators:
- HTTP POST requests to setup.cgi with suspicious ntp_server values
- Outbound connections from router to unexpected destinations
SIEM Query:
source="router" AND (url="*setup.cgi*" AND (param="*ntp_server*" AND value="*;*" OR value="*|*" OR value="*`*"))