CVE-2021-1320
📋 TL;DR
This vulnerability allows authenticated remote attackers to execute arbitrary code as root or cause denial of service on affected Cisco Small Business routers. Attackers with administrator credentials can exploit improper input validation in the web management interface via 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 into connected networks.
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 credential management and network segmentation prevent attackers from accessing the management interface.
🎯 Exploit Status
Exploitation requires valid administrator credentials but is straightforward once credentials are obtained. The vulnerability is in the web interface accessible via HTTP/HTTPS.
🛠️ 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. Log into router web interface. 2. Navigate to Administration > Firmware Upgrade. 3. Download appropriate firmware from Cisco support site. 4. Upload and install firmware. 5. Reboot router after installation completes.
🔧 Temporary Workarounds
Restrict Management Interface Access
allLimit access to the web management interface to trusted IP addresses only
Disable Remote Management
allTurn off web management interface access from WAN/Internet if not required
🧯 If You Can't Patch
- Implement strict credential policies with complex passwords and multi-factor authentication if supported
- Segment router management interface on separate VLAN with strict firewall rules
🔍 How to Verify
Check if Vulnerable:
Check router firmware version via web interface: System Summary > Firmware Version and compare with Cisco advisoryCheck Version:
No CLI command; use web interface at https://[router-ip]/Verify Fix Applied:
Confirm firmware version matches or exceeds fixed versions listed in Cisco advisory📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts followed by successful login and unusual HTTP POST requests to management endpoints
- Device reboot logs without scheduled maintenance
Network Indicators:
- Unusual HTTP traffic patterns to router management interface from unexpected sources
- Multiple device reboots in short timeframes
SIEM Query:
source="router_logs" AND (event="authentication_success" AND src_ip NOT IN trusted_ips) OR (event="device_reboot" AND NOT maintenance_window)