CVE-2019-20488
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary commands on NETGEAR WNR1000V4 routers through command injection in the web management interface. Attackers can exploit this by sending specially crafted requests to the setup.cgi endpoint with shell metacharacters in parameters like sysDNSHost. All users of affected router versions are at risk.
💻 Affected Systems
- NETGEAR WNR1000V4
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the router allowing attackers to install persistent backdoors, intercept network traffic, pivot to internal networks, and use the device for botnet activities.
Likely Case
Remote code execution leading to router configuration changes, DNS hijacking, credential theft, and denial of service.
If Mitigated
Limited impact if the router is behind a firewall with restricted WAN access and web interface disabled.
🎯 Exploit Status
Exploitation requires no authentication and uses simple HTTP requests with command injection payloads.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check NETGEAR for latest firmware updates
Vendor Advisory: https://kb.netgear.com/000061740/Security-Advisory-for-Pre-Authentication-Command-Injection-on-Some-Routers-PSV-2019-0016
Restart Required: Yes
Instructions:
1. Log into router web interface. 2. Navigate to Advanced > Administration > Router Update. 3. Check for updates and apply latest firmware. 4. Reboot router after update.
🔧 Temporary Workarounds
Disable Remote Management
allPrevent WAN access to web management interface
Restrict Web Interface Access
allUse firewall rules to limit access to web interface from trusted IPs only
🧯 If You Can't Patch
- Replace affected router with a supported model
- Place router behind a firewall that blocks all inbound traffic to port 80/443
🔍 How to Verify
Check if Vulnerable:
Check router firmware version via web interface or test with proof-of-concept exploit (not recommended in production).Check Version:
curl -s http://router-ip/ | grep -i firmware || login to web interface and check versionVerify Fix Applied:
Verify firmware version is updated beyond vulnerable version and test that command injection no longer works.📡 Detection & Monitoring
Log Indicators:
- HTTP requests to setup.cgi with shell metacharacters in parameters
- Unusual command execution in router logs
Network Indicators:
- HTTP POST requests to /setup.cgi with suspicious parameter values
- Outbound connections from router to unexpected destinations
SIEM Query:
http.url:"/setup.cgi" AND (http.param:"sysDNSHost=*;*" OR http.param:"sysDNSHost=*|*" OR http.param:"sysDNSHost=*`*" OR http.param:"sysDNSHost=*$(*")