CVE-2021-1346
📋 TL;DR
This vulnerability allows authenticated attackers with administrator credentials to execute arbitrary code as root or cause denial of service on affected Cisco Small Business routers. Attackers can exploit improper input validation in the web management interface by sending crafted HTTP requests. Organizations using Cisco RV016, RV042, RV042G, RV082, RV320, or RV325 routers are affected.
💻 Affected Systems
- Cisco RV016
- Cisco RV042
- Cisco RV042G
- Cisco RV082
- Cisco RV320
- Cisco RV325
📦 What is this software?
Rv016 Multi Wan Vpn Router Firmware by Cisco
View all CVEs affecting Rv016 Multi Wan Vpn Router Firmware →
Rv042 Dual Wan Vpn Router Firmware by Cisco
View all CVEs affecting Rv042 Dual Wan Vpn Router Firmware →
Rv042g Dual Gigabit Wan Vpn Router Firmware by Cisco
View all CVEs affecting Rv042g Dual Gigabit Wan Vpn Router Firmware →
Rv082 Dual Wan Vpn Router Firmware by Cisco
View all CVEs affecting Rv082 Dual Wan Vpn Router Firmware →
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise with root-level arbitrary code execution, allowing full control of the router, network traffic interception, and lateral movement to connected systems.
Likely Case
Denial of service through device reboots disrupting network connectivity, potentially combined with limited code execution for persistence or reconnaissance.
If Mitigated
No impact if proper network segmentation, credential management, and patching are implemented to prevent authenticated attackers from accessing the management interface.
🎯 Exploit Status
Exploitation requires valid admin credentials but is straightforward once obtained. Public exploit code exists.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Cisco advisory for specific fixed versions per model
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-rv-overflow-ghZP68yj
Restart Required: Yes
Instructions:
1. Access router web interface. 2. Navigate to Administration > Firmware Upgrade. 3. Download appropriate firmware from Cisco. 4. Upload and install firmware. 5. Reboot router.
🔧 Temporary Workarounds
Restrict Management Interface Access
allLimit web management interface access to trusted IP addresses only
Configure firewall rules to restrict access to router management IP/ports
Disable Remote Management
allTurn off web-based management from WAN/Internet interfaces
Disable 'Remote Management' in router administration settings
🧯 If You Can't Patch
- Implement strict network segmentation to isolate routers from untrusted networks
- Enforce strong credential policies and multi-factor authentication for admin accounts
🔍 How to Verify
Check if Vulnerable:
Check router firmware version against Cisco advisory. If version is older than fixed release, device is vulnerable.Check Version:
Login to web interface > Status > Router > Firmware VersionVerify Fix Applied:
Confirm firmware version matches or exceeds fixed version listed in Cisco advisory.📡 Detection & Monitoring
Log Indicators:
- Unusual HTTP POST requests to management interface
- Multiple authentication attempts followed by crafted requests
- Router reboot logs without administrative action
Network Indicators:
- Crafted HTTP requests to router management port (typically 443/8443)
- Traffic patterns suggesting buffer overflow attempts
SIEM Query:
source="router_logs" AND (http_method="POST" AND uri="/path/to/vulnerable_endpoint" AND content_length>threshold)