CVE-2022-27947: Netgear R8500 Firmware RCE Vulnerability

CVE-2022-27947 Overview

CVE-2022-27947 is a command injection vulnerability affecting NETGEAR R8500 routers running firmware version 1.0.2.158. The vulnerability allows remote authenticated users to execute arbitrary commands on the affected device by injecting shell metacharacters into specific parameters of the ipv6_fix.cgi script. Attackers can exploit vulnerable parameters including ipv6_wan_ipaddr, ipv6_lan_ipaddr, ipv6_wan_length, and ipv6_lan_length to run malicious commands such as telnetd.

Critical Impact

Authenticated attackers can achieve full remote code execution on the router, potentially gaining persistent access, intercepting network traffic, or using the compromised device as a pivot point for further attacks within the network.

Affected Products

• NETGEAR R8500 Firmware version 1.0.2.158
• NETGEAR R8500 Hardware

Discovery Timeline

• 2022-03-26 - CVE-2022-27947 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-27947

Vulnerability Analysis

This command injection vulnerability (CWE-78: Improper Neutralization of Special Elements used in an OS Command) exists in the IPv6 configuration handler of the NETGEAR R8500 router's web interface. The ipv6_fix.cgi script fails to properly sanitize user-supplied input before passing it to system shell commands.

When an authenticated user submits configuration changes through the router's web interface, the CGI script processes the IPv6 address and prefix length parameters without adequate validation. This allows attackers to append shell metacharacters (such as ;, |, &&, or backticks) followed by arbitrary commands to the legitimate parameter values. The underlying system then executes these injected commands with the privileges of the web server process, typically running as root on embedded devices.

The vulnerability requires authentication, meaning an attacker must first obtain valid credentials to the router's administration interface. However, given the prevalence of default credentials on consumer routers and the potential for credential theft through other means, this authentication requirement provides limited protection in practice.

Root Cause

The root cause of CVE-2022-27947 is improper input validation in the ipv6_fix.cgi script. The vulnerable parameters—ipv6_wan_ipaddr, ipv6_lan_ipaddr, ipv6_wan_length, and ipv6_lan_length—are passed directly to shell commands without sanitization or escaping of special characters. This classic command injection pattern allows user input to break out of its intended context and execute arbitrary system commands.

Attack Vector

The attack is network-based and requires low-privilege authentication to the router's web administration interface. An attacker with valid credentials can craft malicious HTTP requests to the ipv6_fix.cgi endpoint, embedding shell metacharacters in the vulnerable parameters. For example, an attacker could inject commands to spawn a telnetd service, create a reverse shell, or download and execute additional malware.

The attack does not require user interaction beyond the initial authentication, and successful exploitation can result in complete compromise of the device's confidentiality, integrity, and availability.

Detection Methods for CVE-2022-27947

Indicators of Compromise

• Unexpected processes running on the router, particularly telnetd or other network services not normally enabled
• Unusual outbound network connections from the router to unknown external IP addresses
• Modified configuration files or unexpected scheduled tasks in the router's file system
• Authentication logs showing access to the ipv6_fix.cgi endpoint with unusual parameter values containing shell metacharacters

Detection Strategies

• Monitor HTTP request logs for the ipv6_fix.cgi endpoint and inspect parameter values for shell metacharacters (;, |, &&, `, $())
• Implement network intrusion detection rules to identify suspicious patterns in traffic destined for the router's web interface
• Deploy endpoint detection solutions capable of monitoring embedded device behavior for anomalous process execution
• Review router logs for unexpected configuration changes or authentication attempts

Monitoring Recommendations

• Enable verbose logging on the NETGEAR R8500 if available and forward logs to a centralized SIEM
• Monitor network traffic for connections to and from the router's management interface from untrusted sources
• Implement network segmentation to limit exposure of router management interfaces to trusted administrative networks only

How to Mitigate CVE-2022-27947

Immediate Actions Required

• Restrict administrative access to the router's web interface to trusted IP addresses or VLANs only
• Change default credentials immediately and use strong, unique passwords for router administration
• Disable remote management features if not required for your network environment
• Monitor for suspicious activity targeting the router's web interface

Patch Information

Check NETGEAR's official support website for firmware updates that address this vulnerability. Users should update to the latest available firmware version for the R8500 router. Refer to the GitHub Vulnerability Report for additional technical details about this vulnerability.

Workarounds

• Implement access control lists (ACLs) on the network to restrict access to the router's management interface to authorized administrators only
• Place the router's management interface on a separate management VLAN that is not accessible from general user networks
• Consider using a firewall in front of the router to filter malicious requests targeting the CGI endpoints
• Disable IPv6 functionality if not required, as this may reduce the attack surface associated with the vulnerable CGI script