CVE-2025-4140
📋 TL;DR
A critical buffer overflow vulnerability in Netgear EX6120 WiFi extender firmware allows remote attackers to execute arbitrary code or crash the device by manipulating the 'host' argument in the sub_30394 function. This affects Netgear EX6120 devices running firmware version 1.0.3.94. The vulnerability is remotely exploitable without authentication.
💻 Affected Systems
- Netgear EX6120 WiFi Range Extender
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, persistence, lateral movement to connected networks, and data exfiltration.
Likely Case
Device crash/denial of service, potential remote code execution leading to botnet recruitment or network foothold.
If Mitigated
Limited to denial of service if exploit fails or device has memory protections, but still causes disruption.
🎯 Exploit Status
Public proof-of-concept exists in GitHub repository. Buffer overflow vulnerabilities in embedded devices are frequently weaponized for botnets.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: https://www.netgear.com/
Restart Required: Yes
Instructions:
1. Check Netgear support site for firmware updates. 2. If update available, download from official Netgear site. 3. Log into device admin interface. 4. Navigate to firmware update section. 5. Upload and apply new firmware. 6. Device will restart automatically.
🔧 Temporary Workarounds
Network Segmentation
allIsolate Netgear EX6120 devices on separate VLAN or network segment to limit attack surface.
Access Control
linuxRestrict management interface access to trusted IP addresses only using firewall rules.
iptables -A INPUT -p tcp --dport 80 -s trusted_ip -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
🧯 If You Can't Patch
- Replace affected devices with updated models or different vendors
- Disable affected devices entirely until patch is available
🔍 How to Verify
Check if Vulnerable:
Log into device web interface, navigate to Advanced > Administration > Firmware Update to check current firmware version.Check Version:
curl -s http://device-ip/currentsetting.htm | grep FirmwareVerify Fix Applied:
Verify firmware version is no longer 1.0.3.94 after update. Check Netgear advisory for fixed version number.📡 Detection & Monitoring
Log Indicators:
- Repeated connection attempts to device management interface
- Unusual traffic patterns to/from EX6120
- Device reboot logs without user action
Network Indicators:
- Unusual outbound connections from EX6120
- Traffic spikes to device management ports
- Scanning activity targeting port 80/tcp on EX6120
SIEM Query:
source="firewall" dest_ip="EX6120_IP" dest_port=80 action="deny" | stats count by src_ip