CVE-2018-21174
📋 TL;DR
This CVE describes a stack-based buffer overflow vulnerability in multiple NETGEAR routers and gateways that allows authenticated users to execute arbitrary code. The vulnerability affects specific firmware versions of D6100, R7500, R7800, R9000, WNDR3700v4, WNDR4300, WNDR4300v2, WNDR4500v3, and WNR2000v5 devices. An attacker with valid credentials can exploit this to potentially gain full control of the affected device.
💻 Affected Systems
- NETGEAR D6100
- NETGEAR R7500
- NETGEAR R7800
- NETGEAR R9000
- NETGEAR WNDR3700v4
- NETGEAR WNDR4300
- NETGEAR WNDR4300v2
- NETGEAR WNDR4500v3
- NETGEAR WNR2000v5
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise leading to persistent backdoor installation, network traffic interception, lateral movement to connected devices, and botnet recruitment.
Likely Case
Local privilege escalation to root/admin access on the router, allowing configuration changes, credential theft, and network monitoring.
If Mitigated
Limited to authenticated users only, reducing exposure to authorized personnel or attackers who have already compromised credentials.
🎯 Exploit Status
Exploitation requires authentication, but buffer overflow techniques for embedded devices are well-documented. The vulnerability has been publicly disclosed with technical details.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: D6100: 1.0.0.57+, R7500: 1.0.0.122+, 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/000055184/Security-Advisory-for-Post-Authentication-Stack-Overflow-on-Some-Routers-and-Gateways-PSV-2017-2625
Restart Required: Yes
Instructions:
1. Log into NETGEAR router admin interface. 2. Navigate to Advanced > Administration > Firmware Update. 3. Check for updates and apply the latest firmware. 4. Reboot the router after update completes. 5. Verify the firmware version matches patched versions listed above.
🔧 Temporary Workarounds
Restrict administrative access
allLimit administrative interface access to trusted IP addresses only
In router admin interface: Advanced > Security > Access Control > Enable Access Control > Add trusted IP ranges
Change default credentials
allEnsure strong, unique administrative passwords are set
In router admin interface: Advanced > Administration > Set Password
🧯 If You Can't Patch
- Isolate affected devices in separate network segments with strict firewall rules
- Implement network monitoring for unusual administrative access patterns or buffer overflow attempts
🔍 How to Verify
Check if Vulnerable:
Log into router admin interface and check firmware version under Advanced > Administration > Router Status. Compare against vulnerable version ranges.Check Version:
Via web interface: Advanced > Administration > Router Status > Firmware VersionVerify Fix Applied:
Verify firmware version matches or exceeds patched versions listed in fix_official.patch_version after update.📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by successful login and buffer overflow patterns
- Unusual administrative access from unexpected IP addresses
- Firmware modification or configuration change logs
Network Indicators:
- Unusual traffic patterns from router to external IPs
- Administrative interface access from non-trusted sources
- Buffer overflow exploit patterns in HTTP requests to router
SIEM Query:
source="router_logs" AND (event_type="authentication" AND result="success") AND (http_request CONTAINS "overflow" OR http_request CONTAINS "buffer")