CVE-2023-20117: Cisco RV320 Firmware RCE Vulnerability

CVE-2023-20117 Overview

CVE-2023-20117 is a command injection vulnerability affecting the web-based management interface of Cisco Small Business RV320 and RV325 Dual Gigabit WAN VPN Routers. The vulnerability allows an authenticated, remote attacker with valid Administrator credentials to inject and execute arbitrary commands on the underlying Linux operating system with root privileges.

This vulnerability exists due to insufficient validation of user-supplied input in the router's web management interface. An attacker who successfully exploits this flaw can gain complete control over the affected device, potentially compromising the entire network segment protected by the router.

Critical Impact

Authenticated attackers can execute arbitrary commands as root on the underlying Linux operating system, enabling full device compromise. Cisco has not released software updates to address this vulnerability.

Affected Products

• Cisco RV320 Dual Gigabit WAN VPN Router (Firmware version 1.5.1.13)
• Cisco RV325 Dual Gigabit WAN VPN VPN Router (Firmware version 1.5.1.13)
• Cisco RV320 Firmware
• Cisco RV325 Firmware

Discovery Timeline

• April 5, 2023 - CVE-2023-20117 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2023-20117

Vulnerability Analysis

This command injection vulnerability (CWE-78) stems from improper neutralization of special elements used in OS commands within the web-based management interface. The affected routers fail to properly validate and sanitize user-supplied input before passing it to system shell commands.

When an authenticated administrator interacts with certain functions in the web management interface, the input is processed without adequate filtering for shell metacharacters or command delimiters. This allows an attacker to craft malicious input that breaks out of the intended command context and executes arbitrary commands.

The vulnerability is classified under CWE-146 (Improper Neutralization of Expression/Command Delimiters) and CWE-78 (Improper Neutralization of Special Elements used in an OS Command), indicating that the root cause involves both delimiter handling issues and general OS command injection weaknesses.

Root Cause

The root cause of CVE-2023-20117 lies in insufficient input validation within the web-based management interface. The affected firmware fails to properly sanitize user-controlled input before incorporating it into operating system commands. Specifically:

1. Input fields in the web management interface accept special characters and shell metacharacters without proper filtering
2. User-supplied data is directly concatenated into system commands without proper escaping or parameterization
3. The application lacks a whitelist-based input validation approach that would restrict input to expected values

This design flaw allows attackers to inject shell commands by including special characters such as semicolons, pipes, backticks, or other command separators in their input.

Attack Vector

The attack vector for this vulnerability requires network access to the router's web management interface and valid Administrator credentials. The attack flow typically involves:

1. The attacker gains or compromises valid Administrator credentials for the target router
2. The attacker authenticates to the web-based management interface
3. The attacker navigates to a vulnerable function within the interface
4. The attacker submits crafted input containing OS command injection payloads
5. The router processes the malicious input without proper sanitization
6. The injected commands execute with root privileges on the underlying Linux system

While the requirement for Administrator credentials provides some barrier to exploitation, credentials may be obtained through password reuse, credential stuffing, phishing attacks, or prior network compromise. The vulnerability enables privilege escalation from authenticated web interface access to full root-level operating system access.

Detection Methods for CVE-2023-20117

Indicators of Compromise

• Unexpected processes running on the router that are not part of normal router operations
• Unusual outbound network connections from the router to external IP addresses
• Suspicious entries in system logs indicating command execution attempts
• Modifications to router configuration that were not authorized by legitimate administrators
• Evidence of credential harvesting or lateral movement originating from the router

Detection Strategies

• Monitor web management interface logs for unusual input patterns containing shell metacharacters (;, |, &&, backticks, $())
• Implement network monitoring to detect anomalous traffic patterns to and from the router management interface
• Review authentication logs for Administrator login attempts from unexpected IP addresses or at unusual times
• Deploy intrusion detection signatures to identify command injection attempts against Cisco RV320/RV325 devices

Monitoring Recommendations

• Enable comprehensive logging on the router's web management interface if available
• Implement centralized log collection to preserve evidence of potential exploitation attempts
• Configure alerts for multiple failed administrative login attempts followed by successful authentication
• Monitor for unexpected DNS queries or outbound connections originating from router IP addresses

How to Mitigate CVE-2023-20117

Immediate Actions Required

• Restrict access to the web-based management interface to trusted IP addresses only using ACLs
• Ensure Administrator credentials are strong, unique, and not shared across multiple devices
• Disable remote management access if not required, limiting administration to local network only
• Consider network segmentation to isolate management interfaces from general network traffic
• Plan for hardware replacement with supported devices that receive security updates

Patch Information

Cisco has not released software updates to address CVE-2023-20117. The affected Cisco Small Business RV320 and RV325 routers are end-of-life products, and Cisco has indicated that no patches will be made available. Organizations using these devices should strongly consider migrating to current-generation routers that receive ongoing security support.

For the latest information, refer to the Cisco Security Advisory.

Workarounds

• Implement strict IP-based access control lists (ACLs) to limit management interface access to specific trusted administrator workstations
• Disable the web-based management interface entirely if command-line management alternatives are viable
• Place the router's management interface on a dedicated, isolated management VLAN
• Deploy a web application firewall (WAF) or reverse proxy in front of the management interface to filter malicious input patterns

# Example: Restrict management interface access (if supported by device)
# Limit web management to specific trusted subnet
access-list 1 permit 192.168.1.0 0.0.0.255
access-list 1 deny any
# Apply to HTTP/HTTPS management services