CVE-2018-21181
📋 TL;DR
This CVE describes a stack-based buffer overflow vulnerability in multiple NETGEAR router, gateway, and extender models. An authenticated attacker can exploit this to potentially execute arbitrary code or cause denial of service. Only users with administrative credentials can trigger this vulnerability.
💻 Affected Systems
- D7800
- EX2700
- EX6200v2
- R7500v2
- R7800
- R9000
- WN2000RPTv3
- WN3000RPv3
- WN3100RPv2
- WNDR3700v4
- WNDR4300
- WNDR4300v2
- WNDR4500v3
- WNR2000v5
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, persistence, and lateral movement within the network
Likely Case
Denial of service causing device reboot or instability, potentially allowing credential theft if combined with other vulnerabilities
If Mitigated
Limited impact due to authentication requirement, but still poses risk from insider threats or compromised credentials
🎯 Exploit Status
Requires authentication, making exploitation more difficult but still feasible with compromised credentials
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Varies by model - see CVE description for specific fixed versions
Vendor Advisory: https://kb.netgear.com/000055177/Security-Advisory-for-Post-Authentication-Stack-Overflow-on-Some-Routers-Gateways-and-Extenders-PSV-2017-2618
Restart Required: Yes
Instructions:
1. Identify your NETGEAR model number. 2. Visit NETGEAR support website. 3. Download the latest firmware for your specific model. 4. Log into router admin interface. 5. Navigate to Advanced > Administration > Firmware Update. 6. Upload and install the downloaded firmware file. 7. Wait for automatic reboot.
🔧 Temporary Workarounds
Disable remote administration
allPrevents external attackers from accessing the admin interface
Use strong unique admin credentials
allReduces risk of credential compromise enabling exploitation
🧯 If You Can't Patch
- Replace affected devices with supported models
- Segment network to isolate vulnerable devices from critical systems
🔍 How to Verify
Check if Vulnerable:
Check router admin interface for model and firmware version, compare against affected versions in CVECheck Version:
Check via router web interface at 192.168.1.1 or routerlogin.net, or use 'nmap -sV' to identify deviceVerify Fix Applied:
Verify firmware version in admin interface matches or exceeds the patched version for your model📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by successful login and unusual POST requests
- Device reboot logs without normal shutdown sequence
Network Indicators:
- Unusual outbound connections from router
- Traffic patterns suggesting device compromise
SIEM Query:
source="router.log" AND (event="authentication success" AND event="POST /" AND bytes>threshold)