CVE-2019-20767
📋 TL;DR
This CVE describes a stack-based buffer overflow vulnerability in multiple NETGEAR routers and modem-routers that allows authenticated users to execute arbitrary code. The vulnerability affects specific firmware versions of D6100, D3600, D6000, R9000, R8900, R7800, WNDR4500v3, WNDR4300v2, WNDR4300, WNDR3700v4, and WNR2000v5 devices. Successful exploitation could lead to complete device compromise.
💻 Affected Systems
- NETGEAR D6100
- NETGEAR D3600
- NETGEAR D6000
- NETGEAR R9000
- NETGEAR R8900
- NETGEAR R7800
- NETGEAR WNDR4500v3
- NETGEAR WNDR4300v2
- NETGEAR WNDR4300
- NETGEAR WNDR3700v4
- NETGEAR WNR2000v5
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
An authenticated attacker gains remote code execution with root privileges, enabling them to install persistent malware, intercept network traffic, pivot to internal networks, or brick the device.
Likely Case
An authenticated malicious insider or compromised account could execute arbitrary code to modify device settings, steal credentials, or establish persistence on the network.
If Mitigated
With proper access controls and network segmentation, impact is limited to the affected device only, preventing lateral movement to other systems.
🎯 Exploit Status
Exploitation requires authentication but buffer overflow techniques are well-understood. No public exploit code is known, but the vulnerability details are public.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: D6100: 1.0.0.60+, D3600: 1.0.0.75+, D6000: 1.0.0.75+, R9000: 1.0.4.26+, R8900: 1.0.4.26+, R7800: 1.0.2.52+, WNDR4500v3: 1.0.0.58+, WNDR4300v2: 1.0.0.58+, WNDR4300: 1.0.2.104+, WNDR3700v4: 1.0.2.102+, WNR2000v5: 1.0.0.66+
Vendor Advisory: https://kb.netgear.com/000060632/Security-Advisory-for-Post-Authentication-Stack-Overflow-on-Some-Routers-and-Modem-Routers-PSV-2018-0116
Restart Required: Yes
Instructions:
1. Log into NETGEAR router web interface. 2. Navigate to Advanced > Administration > Firmware Update. 3. Check for updates or manually download firmware from NETGEAR support site. 4. Upload and install the latest firmware. 5. Reboot the device after installation completes.
🔧 Temporary Workarounds
Restrict Administrative Access
allLimit administrative access to trusted IP addresses only and disable remote administration if not needed.
Strong Authentication Enforcement
allEnforce strong, unique passwords for all administrative accounts and enable multi-factor authentication if supported.
🧯 If You Can't Patch
- Segment affected devices on isolated network VLANs to limit potential lateral movement
- Implement strict access controls and monitor for unusual authentication attempts or configuration changes
🔍 How to Verify
Check if Vulnerable:
Check current firmware version in router web interface under Advanced > Administration > Firmware Update or via command: telnet [router_ip] (if enabled) and check versionCheck Version:
Check web interface or use: curl -s http://[router_ip]/currentsetting.htm | grep FirmwareVerify Fix Applied:
Verify firmware version matches or exceeds patched versions listed in vendor advisory📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by successful login
- Unusual configuration changes
- Firmware modification logs
- Buffer overflow error messages in system logs
Network Indicators:
- Unusual outbound connections from router
- Traffic to known malicious IPs from router
- Unexpected administrative protocol traffic
SIEM Query:
source="router_logs" AND (event_type="authentication" AND result="success") AND (user="admin" OR user="root") AND (src_ip NOT IN [trusted_ips])