CVE-2023-20118 Cisco Small Business RV Series Routers Command Injection

CVE-2023-20118 is a critical command injection vulnerability discovered in Cisco Small Business RV Series Routers, including models RV016, RV042, RV042G, RV082, RV320, and RV325.

The vulnerability exists due to improper validation of user input in the routers’ web-based management interface. An authenticated, remote attacker with administrative credentials can exploit this flaw by sending maliciously crafted HTTP requests. If successful, this could allow the attacker to execute arbitrary commands with root-level privileges on the device.

This flaw is particularly dangerous because gaining root access allows an attacker to fully compromise the affected router, modify its configurations, eavesdrop on network traffic, and even use it as a launchpad for further attacks.

Cisco has confirmed that these routers have reached End-of-Life (EoL), meaning no security patches will be released to fix this vulnerability.

What is Vulnerable to CVE-2023-20118?

The following Cisco Small Business Router models are vulnerable:

• RV016 Multi-WAN VPN Router
• RV042 Dual WAN VPN Router
• RV042G Dual Gigabit WAN VPN Router
• RV082 Dual WAN VPN Router
• RV320 Dual Gigabit WAN VPN Router
• RV325 Dual Gigabit WAN VPN Router

All firmware versions of these models are affected. Since they are EoL products, Cisco will not provide patches or updates to mitigate this flaw.

If your network is still using any of these models, immediate action is required to secure your environment.

Mitigation and Remediation for CVE-2023-20118

Since no patches will be released, network administrators should take the following immediate actions to mitigate the risk:

1. Disable Remote Management (Recommended)

The web-based management interface is the attack vector for this vulnerability. Disabling it significantly reduces risk.

To disable remote management:

1. Log in to the router’s web-based management interface.
2. Navigate to Firewall > General.
3. Uncheck the Remote Management option.

2. Restrict Access to Management Ports

Blocking external access to ports 443 and 60443 will prevent attackers from exploiting this vulnerability.

• Configure firewall rules to deny inbound traffic on these ports.
• Restrict access to trusted internal networks only.

3. Upgrade to a Supported Router

Since no fix will be provided, the best long-term solution is to replace these routers with Cisco-supported models that receive regular security updates.

Impact of Successful Exploitation of CVE-2023-20118

If an attacker successfully exploits CVE-2023-20118, they can:

• Gain root-level access to the router.
• Execute arbitrary system commands remotely.
• Modify firewall rules and open backdoors.
• Monitor and intercept network traffic.
• Use the router for lateral movement within the network.
• Deploy malware or launch further attacks against internal devices.

Since these routers control internet traffic in small business environments, a compromise could severely impact business operations, leading to data breaches, unauthorized access, or network downtime.

Proof of Concept for CVE-2023-20118

Security researchers have demonstrated proof-of-concept (PoC) exploits where an attacker can send crafted HTTP requests containing malicious system commands. Since the web interface does not properly sanitize input, the router executes the attacker’s commands with root privileges.

A typical PoC attack might look like this:

This example injects a Linux command (id) to check if the attacker has gained root access. If successful, the router returns a response proving the exploit worked.

Although Cisco has not released official PoCs, cybersecurity experts have warned that exploits could become publicly available, putting businesses at high risk.

CVE-2023-20118 is a severe security vulnerability affecting Cisco Small Business RV Series Routers. Since these devices have reached End-of-Life, Cisco will not provide a patch, making it essential for users to disable remote management, restrict access, and replace vulnerable routers as soon as possible.