CVE-2018-21175
📋 TL;DR
This CVE describes a stack-based buffer overflow vulnerability in certain NETGEAR routers and gateways that allows an authenticated attacker to execute arbitrary code. The vulnerability affects multiple NETGEAR device models running outdated firmware versions. Exploitation requires authentication but could lead to complete device compromise.
💻 Affected Systems
- NETGEAR D6100
- NETGEAR R6100
- NETGEAR R7800
- NETGEAR R9000
- NETGEAR WNDR3700v4
- NETGEAR WNDR4300
- NETGEAR WNDR4300v2
- NETGEAR WNDR4500v3
- NETGEAR WNR2000v5
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
An authenticated attacker could execute arbitrary code with root privileges, potentially taking full control of the device, intercepting network traffic, or using it as a pivot point into the internal network.
Likely Case
An attacker with valid credentials could crash the device or execute limited code, potentially disrupting network services or gaining persistent access.
If Mitigated
With proper access controls and updated firmware, the risk is minimal as the vulnerability requires authentication and has been patched.
🎯 Exploit Status
Exploitation requires authentication, which adds a barrier but not complete protection. Stack-based buffer overflows are well-understood attack vectors.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: D6100: 1.0.0.57+, R6100: 1.0.1.20+, 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/000055183/Security-Advisory-for-Post-Authentication-Stack-Overflow-on-Some-Routers-and-Gateways-PSV-2017-2624
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 device after update completes.
🔧 Temporary Workarounds
Restrict administrative access
allLimit administrative interface access to trusted IP addresses only
Configure firewall rules to restrict access to router admin interface (typically port 80/443)
Strong authentication controls
allImplement strong, unique passwords and consider disabling remote administration
Change default admin password to complex, unique password
Disable remote administration if not needed
🧯 If You Can't Patch
- Replace affected devices with supported models if firmware updates are no longer available
- Segment affected devices in isolated network zones to limit potential damage
🔍 How to Verify
Check if Vulnerable:
Check current firmware version in router admin interface under Advanced > Administration > Firmware Update and compare with patched versionsCheck Version:
Log into router admin interface and navigate to Advanced > Administration > Firmware Update to view current versionVerify Fix Applied:
Verify firmware version matches or exceeds the patched version listed in the vendor advisory📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by successful login and unusual process activity
- Router crash logs or unexpected reboots
Network Indicators:
- Unusual outbound connections from router to unknown destinations
- Changes to router configuration without authorized change requests
SIEM Query:
source="router_logs" AND (event="authentication_success" AND user="admin" AND src_ip NOT IN trusted_ips) OR event="device_reboot"