CVE-2023-20118: Cisco RV016 Firmware RCE Vulnerability

CVE-2023-20118 Overview

CVE-2023-20118 is a command injection vulnerability in the web-based management interface of multiple Cisco Small Business Router models. This vulnerability allows an authenticated, remote attacker to execute arbitrary commands with root-level privileges on affected devices. The flaw stems from improper validation of user input within incoming HTTP packets, enabling attackers with valid administrative credentials to send crafted HTTP requests that bypass security controls.

Critical Impact

This vulnerability is actively exploited in the wild and has been added to CISA's Known Exploited Vulnerabilities (KEV) catalog. Cisco has confirmed they will not release patches for these end-of-life devices, leaving organizations with no vendor-supported remediation path.

Affected Products

• Cisco RV016 Multi-WAN VPN Router (all firmware versions)
• Cisco RV042 Dual WAN VPN Router (all firmware versions)
• Cisco RV042G Dual Gigabit WAN VPN Router (all firmware versions)
• Cisco RV082 Dual WAN VPN Router (all firmware versions)
• Cisco RV320 Dual Gigabit WAN VPN Router (all firmware versions)
• Cisco RV325 Dual Gigabit WAN VPN Router (all firmware versions)

Discovery Timeline

• April 13, 2023 - CVE-2023-20118 published to NVD
• October 28, 2025 - Last updated in NVD database

Technical Details for CVE-2023-20118

Vulnerability Analysis

This command injection vulnerability (CWE-77) exists within the HTTP request handling mechanism of the web-based management interface. When processing incoming HTTP packets, the affected routers fail to properly sanitize user-supplied input before passing it to system shell commands. This allows an authenticated attacker to inject arbitrary operating system commands that execute with root privileges.

The vulnerability is particularly concerning because it provides complete system-level access once exploited. An attacker who gains root privileges can access unauthorized data, modify device configurations, intercept network traffic, pivot to internal network resources, or use the compromised device as a launching point for further attacks.

While authentication is required to exploit this vulnerability, the combination of network accessibility and the potential for credential theft or weak password usage makes this a significant risk. The fact that these devices are actively targeted by threat actors, as evidenced by CISA's KEV listing, underscores the urgency of addressing this security gap.

Root Cause

The root cause of CVE-2023-20118 is improper input validation in the web-based management interface. User-supplied data from HTTP requests is incorporated into system commands without adequate sanitization or escaping. This allows specially crafted input containing shell metacharacters and command sequences to be interpreted and executed by the underlying operating system shell.

Attack Vector

The attack is conducted remotely over the network by sending malicious HTTP requests to the web-based management interface. The attacker must first obtain valid administrative credentials for the target device. Once authenticated, the attacker crafts an HTTP request containing embedded command injection payloads within parameters that are processed by vulnerable backend scripts or binaries.

Upon receiving the crafted request, the vulnerable router passes the malicious input to shell command execution functions without proper validation. The injected commands execute with root privileges, granting the attacker full control over the device. This can be leveraged to establish persistence, exfiltrate configuration data including credentials, or compromise the broader network infrastructure.

Detection Methods for CVE-2023-20118

Indicators of Compromise

• Unexpected outbound connections from router management interfaces to unknown external IP addresses
• Anomalous HTTP request patterns to the web management interface containing shell metacharacters (;, |, &, $(), backticks)
• Unauthorized configuration changes or new user accounts on affected devices
• Unusual process activity or network traffic originating from the router

Detection Strategies

• Monitor authentication logs for unusual login attempts or successful authentications from unexpected source IPs
• Implement network-based intrusion detection rules to identify HTTP requests containing command injection patterns targeting Cisco Small Business Router management interfaces
• Deploy SIEM correlation rules to detect authentication to router management interfaces followed by anomalous device behavior
• Review router logs for evidence of command execution or system-level modifications

Monitoring Recommendations

• Enable comprehensive logging on all affected Cisco Small Business Routers and forward logs to a centralized SIEM platform
• Implement network flow monitoring to baseline normal traffic patterns and alert on deviations
• Deploy endpoint detection and response (EDR) solutions with network visibility capabilities to monitor for lateral movement from compromised network devices
• Establish alerts for any access to router management interfaces from non-authorized IP ranges

How to Mitigate CVE-2023-20118

Immediate Actions Required

• Disable remote management access to affected routers immediately if not operationally required
• Restrict management interface access to trusted internal IP addresses only using access control lists (ACLs)
• Implement strong, unique administrative credentials on all affected devices
• Plan replacement of affected end-of-life devices with currently supported models
• Segment network to isolate affected routers from critical assets

Patch Information

Cisco has explicitly stated they will not release software updates to address this vulnerability. The affected router models have reached end-of-life status and are no longer supported. Organizations should prioritize replacement of these devices with currently supported router models that receive security updates. Refer to the Cisco Security Advisory for complete details and official guidance from Cisco.

Workarounds

• Disable the remote management feature entirely as recommended by Cisco in their security advisory
• Implement network-level access controls to restrict management interface access to specific trusted IP addresses
• Place affected routers behind a firewall with strict ingress filtering to prevent unauthorized access to management ports
• Consider implementing a VPN requirement for any administrative access to these devices
• Monitor the CISA KEV Catalog entry for updated threat intelligence

# Example ACL configuration to restrict management access (device-specific syntax may vary)
# Restrict web management to internal admin network only
access-list 101 permit tcp 10.0.10.0 0.0.0.255 any eq 443
access-list 101 deny tcp any any eq 443
access-list 101 deny tcp any any eq 80