CVE-2021-38516
📋 TL;DR
This CVE describes a missing function-level access control vulnerability in numerous NETGEAR routers, gateways, and WiFi systems. It allows attackers to bypass authentication and access administrative functions without proper credentials. Users with affected devices running vulnerable firmware versions are at risk.
💻 Affected Systems
- NETGEAR D6220
- D6400
- D7000v2
- D7800
- D8500
- DC112A
- DGN2200v4
- RBK50
- RBR50
- RBS50
- RBK20
- RBR20
- RBS20
- RBK40
- RBR40
- RBS40
- R6020
- R6080
- R6120
- R6220
- R6230
- R6250
- R6260
- R6850
- R6350
- R6400v2
- R6700v3
- R6700v2
- R6800
- R6900v2
- R7000
- R6900P
- R7000P
- R7100LG
- R7200
- R7350
- R7400
- R7450
- AC2100
- AC2400
- AC2600
- R7500v2
- R7800
- R7900
- R7960P
- R8000
- R7900P
- R8000P
- R8900
- R9000
- RAX120
- RBK752
- RBR750
- RBS750
- RBK852
- RBR850
- RBS850
- WNR3500Lv2
- XR450
- XR500
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attacker to reconfigure network settings, intercept traffic, install malware, or use device as part of botnet.
Likely Case
Unauthorized access to administrative functions leading to network configuration changes, DNS hijacking, or credential theft.
If Mitigated
Limited impact if device is behind firewall with strict access controls and network segmentation.
🎯 Exploit Status
The vulnerability allows authentication bypass, making exploitation straightforward once the attack vector is identified.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions specified in CVE description (e.g., D6220 1.0.0.48+, D6400 1.0.0.82+, etc.)
Vendor Advisory: https://kb.netgear.com/000063780/Security-Advisory-for-Missing-Function-Level-Access-Control-on-Some-Routers-Gateways-and-WiFi-Systems-PSV-2020-0273
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 router admin interface. 5. Navigate to firmware update section. 6. Upload and install new firmware. 7. Reboot device after installation.
🔧 Temporary Workarounds
Disable remote administration
allPrevents external attackers from accessing admin interface over internet
Log into router admin interface -> Advanced -> Remote Management -> Disable
Change default admin credentials
allMitigates risk if authentication bypass is partial or requires some credentials
Log into router admin interface -> Advanced -> Administration -> Set Password -> Change password
🧯 If You Can't Patch
- Place device behind firewall with strict access controls to limit exposure
- Implement network segmentation to isolate vulnerable device from critical systems
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router admin interface under Advanced -> Administration -> Router Status or Firmware UpdateCheck Version:
No CLI command - check via web interface at http://routerlogin.net or http://192.168.1.1Verify Fix Applied:
Confirm firmware version matches or exceeds patched versions listed in CVE description📡 Detection & Monitoring
Log Indicators:
- Unauthorized access attempts to admin pages
- Configuration changes from unexpected IP addresses
- Multiple failed login attempts followed by successful access
Network Indicators:
- Unusual traffic patterns to router admin interface
- DNS configuration changes
- Port scans targeting router management ports
SIEM Query:
source="router_logs" AND (event="admin_access" OR event="config_change") AND user="unknown" OR ip!=internal_range