CVE-2018-21093
📋 TL;DR
CVE-2018-21093 is a stack-based buffer overflow vulnerability affecting multiple NETGEAR routers, modem-routers, wireless extenders, and Orbi satellites. Unauthenticated attackers can exploit this vulnerability remotely, potentially gaining control of affected devices. The vulnerability affects numerous NETGEAR models with firmware versions below specific thresholds.
💻 Affected Systems
- NETGEAR D8500
- EX3700
- EX3800
- EX6000
- EX6100
- EX6120
- EX6130
- EX6150
- EX6200
- EX7000
- R6250
- R6300-2CXNAS
- R6300v2
- R6400
- R6400v2
- R6700
- R6900
- R7000
- R7000P
- R6900P
- R7100LG
- R7300
- R7900
- R8000
- R8000P
- R7900P
- R8500
- R8300
- RBW30
- WN2500RPv2
- WNR3500Lv2
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing remote code execution, enabling attackers to intercept network traffic, install malware, pivot to internal networks, or create persistent backdoors.
Likely Case
Device crash/reboot causing denial of service, potentially followed by remote code execution if exploit is weaponized.
If Mitigated
No impact if devices are patched or properly segmented behind firewalls with restricted WAN access.
🎯 Exploit Status
Exploitation requires no authentication and has been publicly documented. The vulnerability is in pre-authentication code, making it easily accessible to attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: See specific fixed versions in CVE description (e.g., D8500 1.0.3.42+, EX3700 1.0.0.70+, etc.)
Restart Required: Yes
Instructions:
1. Identify your NETGEAR device model
2. Visit NETGEAR support website
3. Download latest firmware for your model
4. Log into device admin interface
5. Navigate to firmware update section
6. Upload and apply the firmware update
7. Device will reboot automatically
🔧 Temporary Workarounds
Network Segmentation
allPlace affected devices behind firewalls with strict inbound rules to limit WAN exposure
Disable Remote Management
allTurn off remote administration features if enabled
🧯 If You Can't Patch
- Replace affected devices with patched models or alternative vendors
- Implement strict network segmentation and firewall rules to isolate vulnerable devices
🔍 How to Verify
Check if Vulnerable:
Check device firmware version via admin web interface and compare against patched versions listed in CVECheck Version:
Login to device admin interface → Advanced → Administration → Firmware Update (exact path varies by model)Verify Fix Applied:
Confirm firmware version matches or exceeds the patched version for your specific model📡 Detection & Monitoring
Log Indicators:
- Unexpected device reboots
- Crash logs in device system logs
- Unusual traffic patterns to/from device
Network Indicators:
- Exploit-specific network traffic patterns (if known)
- Unexpected connections to device management interfaces
SIEM Query:
Search for: device_type="NETGEAR" AND (event_type="crash" OR event_type="reboot") AND firmware_version < [patched_version]🔗 References
- https://kb.netgear.com/000060456/Security-Advisory-for-Pre-Authentication-Stack-Overflow-on-Some-Routers-Modem-Routers-Wireless-Extenders-and-Orbi-Satellites-PSV-2017-2011
- https://kb.netgear.com/000060456/Security-Advisory-for-Pre-Authentication-Stack-Overflow-on-Some-Routers-Modem-Routers-Wireless-Extenders-and-Orbi-Satellites-PSV-2017-2011
