CVE-2021-27251
📋 TL;DR
This vulnerability allows network-adjacent attackers to execute arbitrary code with root privileges on NETGEAR Nighthawk R7800 routers by exploiting insecure firmware update protocols. No authentication is required, making it accessible to anyone on the same network. Affected users are those with vulnerable NETGEAR router installations.
💻 Affected Systems
- NETGEAR Nighthawk R7800
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the router with root-level code execution, allowing attackers to intercept traffic, modify configurations, install persistent malware, or pivot to other network devices.
Likely Case
Router takeover leading to man-in-the-middle attacks, DNS hijacking, credential theft from network traffic, and potential compromise of connected devices.
If Mitigated
Limited impact if router is isolated from critical systems and network segmentation prevents lateral movement.
🎯 Exploit Status
Exploitation requires network adjacency but no authentication. The vulnerability is in the firmware update mechanism's fallback to insecure protocols.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firmware version 1.0.2.68 or later
Vendor Advisory: https://kb.netgear.com/000062883/Security-Advisory-for-Multiple-Vulnerabilities-on-Some-Routers-Satellites-and-Extenders
Restart Required: Yes
Instructions:
1. Log into router admin interface. 2. Navigate to Advanced > Administration > Firmware Update. 3. Check for updates and install firmware version 1.0.2.68 or later. 4. Reboot router after installation.
🔧 Temporary Workarounds
Disable remote management
allPrevents external access to router administration interface
Network segmentation
allIsolate router from critical systems using VLANs or firewall rules
🧯 If You Can't Patch
- Replace router with a patched model or different vendor
- Implement strict network access controls to limit adjacent network access
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface under Advanced > Administration > Firmware UpdateCheck Version:
Not applicable - check via web interfaceVerify Fix Applied:
Confirm firmware version is 1.0.2.68 or later in router admin interface📡 Detection & Monitoring
Log Indicators:
- Unusual firmware update attempts
- Unexpected reboots
- Unknown processes running on router
Network Indicators:
- Unexpected HTTP/HTTPS traffic to router on update ports
- Suspicious DNS queries from router
SIEM Query:
Not applicable - router logs typically not integrated into SIEM🔗 References
- https://kb.netgear.com/000062883/Security-Advisory-for-Multiple-Vulnerabilities-on-Some-Routers-Satellites-and-Extenders
- https://www.zerodayinitiative.com/advisories/ZDI-21-247/
- https://kb.netgear.com/000062883/Security-Advisory-for-Multiple-Vulnerabilities-on-Some-Routers-Satellites-and-Extenders
- https://www.zerodayinitiative.com/advisories/ZDI-21-247/
