CVE-2022-20708: Cisco RV340 Firmware RCE Vulnerability

CVE-2022-20708 Overview

CVE-2022-20708 affects multiple Cisco Small Business RV160, RV260, RV340, and RV345 Series Routers with critical security flaws that could allow attackers to execute arbitrary code, elevate privileges, execute arbitrary commands, bypass authentication and authorization protections, fetch and run unsigned software, or cause denial of service (DoS). This vulnerability is part of a series of security issues affecting the web-based management interface and related components of these widely deployed small business network devices.

Critical Impact

This vulnerability is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, indicating active exploitation in the wild. Attackers with adjacent network access and low privileges can achieve complete compromise of affected router devices, gaining full control over network traffic and infrastructure.

Affected Products

• Cisco RV340 Dual WAN Gigabit VPN Router (Firmware)
• Cisco RV340W Dual WAN Gigabit Wireless-AC VPN Router (Firmware)
• Cisco RV345 Dual WAN Gigabit VPN Router (Firmware)
• Cisco RV345P Dual WAN Gigabit POE VPN Router (Firmware)

Discovery Timeline

• 2022-02-10 - CVE-2022-20708 published to NVD
• 2025-10-28 - Last updated in NVD database

Technical Details for CVE-2022-20708

Vulnerability Analysis

This vulnerability encompasses multiple security weaknesses including Stack-based Buffer Overflow (CWE-121) and OS Command Injection (CWE-78). The flaws exist within the web-based management interface and underlying firmware of affected Cisco Small Business routers. An attacker positioned on an adjacent network segment with low-level credentials can exploit these vulnerabilities to achieve complete device compromise.

The Stack-based Buffer Overflow component (CWE-121) allows attackers to write beyond the allocated buffer boundaries on the stack, potentially overwriting return addresses and gaining control of program execution. The OS Command Injection component (CWE-78) enables attackers to inject and execute arbitrary operating system commands through improperly sanitized input fields in the web management interface.

Root Cause

The root causes of CVE-2022-20708 are twofold:

1. Insufficient Input Validation: The web-based management interface fails to properly validate and sanitize user-supplied input before processing, allowing specially crafted requests to inject malicious commands.

2. Improper Buffer Size Handling: Memory allocation routines do not adequately verify buffer boundaries when processing input data, leading to stack-based buffer overflow conditions that can corrupt adjacent memory regions.

These architectural weaknesses in the firmware's input handling routines allow attackers to bypass intended security controls and execute arbitrary code with elevated privileges on the underlying operating system.

Attack Vector

The attack requires adjacent network access, meaning the attacker must be on the same network segment as the target device or able to reach it through a connected network. With low-privilege authentication (such as a guest or read-only user account), the attacker can craft malicious HTTP requests targeting vulnerable endpoints in the web management interface.

The exploitation chain typically involves:

1. Gaining access to the adjacent network segment containing the target router
2. Authenticating to the web management interface with minimal privileges
3. Sending specially crafted requests containing malicious payloads
4. Triggering either the buffer overflow or command injection vulnerability
5. Achieving code execution with root privileges on the router

Successful exploitation grants the attacker full administrative control over the router, enabling traffic interception, network pivot attacks, and persistent access to the compromised network infrastructure.

Detection Methods for CVE-2022-20708

Indicators of Compromise

• Unexpected administrative account creation or privilege modifications on affected routers
• Unusual outbound network connections from router management interfaces
• Anomalous log entries indicating repeated failed authentication attempts followed by successful access
• Presence of unauthorized firmware modifications or unsigned software components
• Unexpected router configuration changes, particularly in NAT rules, firewall policies, or VPN settings

Detection Strategies

• Monitor web management interface access logs for requests with unusually long parameter values or special characters indicative of injection attempts
• Implement network traffic analysis to detect exploitation attempts targeting HTTP/HTTPS management ports (typically 443, 8443)
• Deploy intrusion detection signatures specific to Cisco RV Series router exploitation attempts
• Establish baseline behavior for router administrative actions and alert on deviations

Monitoring Recommendations

• Enable comprehensive logging on all affected Cisco Small Business routers and forward logs to a centralized SIEM
• Implement network segmentation to isolate router management interfaces from general user traffic
• Deploy network monitoring solutions to track all traffic to and from router management interfaces
• Configure alerts for any configuration changes or firmware updates on affected devices

How to Mitigate CVE-2022-20708

Immediate Actions Required

• Apply Cisco's security patches immediately by upgrading to the latest firmware version for affected router models
• Restrict access to the web-based management interface to trusted IP addresses only
• Implement strong authentication policies and disable unnecessary user accounts on affected devices
• Isolate affected routers on a dedicated management VLAN with strict access controls
• Review router configurations and logs for signs of compromise before and after patching

Patch Information

Cisco has released firmware updates addressing these vulnerabilities. Administrators should consult the Cisco Security Advisory for specific version information and download links. Additional technical analysis is available through the Zero Day Initiative Advisory. Given this vulnerability is listed in the CISA Known Exploited Vulnerabilities Catalog, immediate patching is strongly recommended.

Workarounds

• Disable remote management access to the web interface if not operationally required
• Implement access control lists (ACLs) to restrict management interface access to specific administrator workstations
• Enable two-factor authentication if supported by the firmware version
• Consider deploying a network-based Web Application Firewall (WAF) in front of the management interface to filter malicious requests

# Example ACL configuration to restrict management access (Cisco CLI)
# Restrict web management to specific trusted IP address
ip access-list extended MGMT-ACCESS
 permit tcp host 192.168.1.10 any eq 443
 deny tcp any any eq 443
 permit ip any any