CVE-2016-6277

What Is NETGEAR Multiple Routers?

NETGEAR is one of the largest home and small business networking equipment vendors globally. The affected router models — including the R7000, R6400, R8000, D6220, D6400, and others — are high-performance 802.11ac (Wi-Fi 5) routers widely deployed in homes and small offices. These routers provide the internet gateway for millions of households and small businesses, controlling all inbound and outbound network traffic, and their embedded Linux web interface manages router configuration.

Embedded consumer router vulnerabilities are among the most persistently exploited device categories: routers are rarely patched, often internet-facing (management interfaces exposed), and provide a privileged network position (all traffic passes through them), making them prime targets for botnet enrollment and traffic interception.

Overview

CVE-2016-6277 is a command injection vulnerability in the web management interface of multiple NETGEAR router models. The web interface allows unauthenticated web pages to pass form input directly to the router's command-line interface without adequate sanitization. An attacker who persuades a user to visit a malicious web page (or exploits the vulnerability directly from the LAN) can inject arbitrary OS commands executed with root privileges on the router. Multiple NETGEAR models are affected. NETGEAR released firmware patches; CISA added CVE-2016-6277 to the KEV catalog in March 2022, reflecting widespread ongoing exploitation by botnets.

Affected Versions

Check NETGEAR's security advisory for the complete list of affected models and the specific patched firmware version for each.

Technical Details

Root Cause: Command Injection via Web Interface

CVE-2016-6277 is a command injection vulnerability (CWE-352 CSRF vector, with underlying OS command injection) in the NETGEAR router web management interface. The router's embedded HTTP server (httpd) processes form submissions from the web interface and passes form field values directly to shell commands without adequate sanitization. Shell metacharacters in the input break out of the intended command context.

CSRF-based exploitation from external web page: When a user with access to the router's web interface visits a malicious external web page, the page executes JavaScript that sends crafted HTTP requests to the router's LAN IP address (typically 192.168.1.1). Because the browser sends requests to the router's domain from the victim's network context, the router processes these as if they came from a legitimate admin session.

Direct LAN exploitation: An attacker already on the local network can send crafted HTTP requests directly to the router's management interface without requiring CSRF.

Command injection payload: A URL like:

http://192.168.1.1/cgi-bin/;uname$IFS-a

causes the router to execute uname -a as root, confirming command injection. More impactful payloads download and execute botnet malware, modify DNS settings, or create backdoor accounts.

Attack Characteristics

Discovery

Publicly disclosed by a security researcher on the Kali-NetHunter forum on December 6, 2016; NETGEAR confirmed the vulnerability and began releasing firmware fixes within days.

Exploitation Context

• Mirai botnet successors: Following the Mirai IoT botnet (which leveraged default credentials), successor botnets targeted known router vulnerabilities including CVE-2016-6277 for recruitment; compromised NETGEAR routers have been enrolled in DDoS botnet networks and used for traffic interception
• DNS hijacking attacks: Compromised home routers are used for DNS hijacking — modifying the router's DNS settings to redirect users to phishing pages for banking, email, and other services; CVE-2016-6277 provides root access enabling DNS configuration modification
• Long exploitation tail: Home router vulnerabilities like CVE-2016-6277 remain exploitable for years because consumers rarely update router firmware; CISA's 2022 KEV addition reflects ongoing exploitation six years after disclosure
• ISP and enterprise edge exposure: Some NETGEAR R-series routers were deployed at small business edge locations with web management interfaces internet-accessible; these configurations expose the management interface directly to attackers without requiring CSRF

Remediation

1. Apply the NETGEAR firmware update — download and install the latest firmware for your specific router model from NETGEAR's support site. Verify the firmware version in the router admin panel post-update.

2. Disable remote management — ensure the router's web management interface is not accessible from the internet (WAN-side). Navigate to router admin → Advanced → Remote Management → Disable.

3. Replace end-of-life routers — if no firmware fix is available for your specific model, replace the device with a currently supported router. NETGEAR R6400 and R7000 have received firmware updates; check NETGEAR's security advisory for your model's status.

4. Change the router admin password — use a strong, unique password for router administration to prevent LAN-side exploitation via web interface.

5. Monitor for DNS hijacking — periodically verify your router's DNS settings match your ISP's or your configured DNS provider; unexpected DNS server addresses may indicate compromise.