CVE-2018-21177
📋 TL;DR
This vulnerability allows an authenticated attacker to trigger a stack-based buffer overflow on affected NETGEAR routers and gateways. Successful exploitation could lead to remote code execution or device crash. Only users with administrative credentials can exploit this vulnerability.
💻 Affected Systems
- NETGEAR D6100
- R6100
- R7800
- R9000
- WNDR3700v4
- WNDR4300
- WNDR4300v2
- WNDR4500v3
- WNR2000v5
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with administrative privileges, allowing complete device takeover, network compromise, and persistent backdoor installation.
Likely Case
Device crash requiring physical reboot, causing temporary network outage and service disruption.
If Mitigated
No impact if proper authentication controls prevent unauthorized access to administrative interfaces.
🎯 Exploit Status
Requires authenticated access to administrative interface. No public exploit code available as of knowledge cutoff.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: D6100 1.0.0.57+, R6100 1.0.1.20+, R7800 1.0.2.40+, R9000 1.0.2.52+, WNDR3700v4 1.0.2.92+, WNDR4300 1.0.2.94+, WNDR4300v2 1.0.0.50+, WNDR4500v3 1.0.0.50+, WNR2000v5 1.0.0.62+
Vendor Advisory: https://kb.netgear.com/000055181/Security-Advisory-for-Post-Authentication-Stack-Overflow-on-Some-Routers-and-Gateways-PSV-2017-2622
Restart Required: Yes
Instructions:
1. Log into router web interface. 2. Navigate to Advanced > Administration > Firmware Update. 3. Check for updates or manually download from NETGEAR support site. 4. Upload firmware file and follow update process. 5. Device will reboot automatically.
🔧 Temporary Workarounds
Restrict Administrative Access
allLimit administrative interface access to trusted IP addresses only
Configure firewall rules to restrict access to router admin port (typically 80/443)
Strong Authentication
allUse complex administrative passwords and enable multi-factor authentication if available
Change default admin password to complex unique password
🧯 If You Can't Patch
- Disable remote administration and only allow local network access to admin interface
- Implement network segmentation to isolate vulnerable devices from critical systems
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router web interface under Advanced > Administration > Firmware UpdateCheck Version:
Check via web interface or use nmap/router scanning tools to identify firmware versionVerify Fix Applied:
Verify firmware version matches or exceeds patched versions listed in advisory📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by successful login
- Unusual administrative access patterns
- Device crash/reboot logs
Network Indicators:
- Unusual traffic to router administrative ports
- Multiple authentication requests to router
SIEM Query:
source="router_logs" AND (event_type="authentication" AND result="success") AND user="admin" AND src_ip NOT IN [trusted_ips]