CVE-2022-20700: Cisco RV340 Firmware RCE Vulnerability

CVE-2022-20700 Overview

CVE-2022-20700 affects multiple Cisco Small Business RV Series Routers, representing a critical stack-based buffer overflow vulnerability that enables remote attackers to execute arbitrary code, elevate privileges, bypass authentication and authorization protections, fetch and run unsigned software, or cause denial of service conditions. This vulnerability is part of a broader set of security issues affecting these widely deployed networking devices commonly found in small business environments.

Critical Impact

This vulnerability is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, indicating confirmed active exploitation in the wild. Unauthenticated remote attackers can achieve complete system compromise through network-based attacks requiring no user interaction.

Affected Products

• Cisco RV160 Series Routers (RV160, RV160W) and associated firmware
• Cisco RV260 Series Routers (RV260, RV260P, RV260W) and associated firmware
• Cisco RV340 Series Routers (RV340, RV340W) and associated firmware
• Cisco RV345 Series Routers (RV345, RV345P) and associated firmware

Discovery Timeline

• February 10, 2022 - CVE-2022-20700 published to NVD
• October 28, 2025 - Last updated in NVD database

Technical Details for CVE-2022-20700

Vulnerability Analysis

This vulnerability stems from memory corruption issues classified under CWE-121 (Stack-based Buffer Overflow) and CWE-787 (Out-of-bounds Write). The affected routers fail to properly validate the length of input data before copying it to fixed-size memory buffers on the stack. When an attacker sends specially crafted requests to the vulnerable web management interface, the excessive data overwrites adjacent memory regions, including return addresses and saved registers.

The network-accessible attack vector requires no authentication or user interaction, making this vulnerability particularly dangerous for internet-facing devices. Successful exploitation grants attackers the ability to execute code with root privileges, effectively providing complete control over the affected router and potentially enabling lateral movement within the network.

Root Cause

The vulnerability originates from insufficient bounds checking in the router's web management interface. Input data processed by the firmware is copied into stack-allocated buffers without proper validation of the data length against the buffer capacity. This oversight allows attackers to overflow the buffer boundaries and corrupt critical control data structures in memory.

Attack Vector

The exploitation path involves sending malicious HTTP requests to the router's web management interface. Since the vulnerability requires no prior authentication, any attacker with network access to the management interface can attempt exploitation. The attack flow typically follows:

1. The attacker identifies a vulnerable Cisco RV Series router with an accessible web management interface
2. A crafted HTTP request containing oversized input data is sent to the vulnerable endpoint
3. The firmware processes the request and copies the malicious input without proper bounds checking
4. The stack buffer overflow corrupts the return address, redirecting code execution
5. Attacker-controlled shellcode executes with root privileges on the device

The vulnerability can be exploited over the network without requiring any form of authentication. Organizations exposing the management interface to untrusted networks face the highest risk. Technical details regarding specific exploitation techniques can be found in the Cisco Security Advisory.

Detection Methods for CVE-2022-20700

Indicators of Compromise

• Unexpected outbound connections from the router to unknown IP addresses
• Unauthorized configuration changes or new administrative accounts on the device
• Unusual system processes or services running on the router
• Evidence of crash logs or unexpected reboots in router diagnostics
• Network traffic anomalies indicating potential command-and-control communication

Detection Strategies

• Monitor web management interface logs for malformed or unusually large HTTP requests
• Implement network-based intrusion detection rules to identify exploitation attempts targeting known vulnerable endpoints
• Deploy network traffic analysis to detect anomalous patterns from router management interfaces
• Conduct regular firmware version audits to identify unpatched devices in your environment

Monitoring Recommendations

• Enable comprehensive logging on all Cisco RV Series routers and forward logs to a centralized SIEM
• Implement network segmentation monitoring to detect unauthorized traffic flows from router management interfaces
• Establish baseline network behavior for router devices and alert on deviations
• Monitor for known exploitation signatures and CISA KEV catalog indicators

How to Mitigate CVE-2022-20700

Immediate Actions Required

• Apply the latest firmware updates from Cisco immediately for all affected RV Series routers
• Disable remote management access or restrict it to trusted IP addresses and VPN connections only
• Implement network segmentation to isolate router management interfaces from untrusted networks
• Review router configurations for unauthorized changes and reset credentials if compromise is suspected

Patch Information

Cisco has released firmware updates to address CVE-2022-20700 and related vulnerabilities. Administrators should consult the Cisco Security Advisory for specific version information and download links. Given this vulnerability's inclusion in the CISA Known Exploited Vulnerabilities Catalog, patching should be treated as an urgent priority.

Workarounds

• Disable the web-based management interface if not required for operations
• Restrict access to the management interface using access control lists (ACLs) to permit only trusted administrative IP addresses
• Place router management interfaces on a dedicated management VLAN with strict access controls
• Use VPN tunnels for remote administration rather than exposing the management interface directly

# Example ACL configuration to restrict management access
# Apply on the router to limit web management to trusted subnet
access-list 10 permit 192.168.1.0 0.0.0.255
access-list 10 deny any log
# Apply to HTTP/HTTPS management interface
ip http access-class 10