CVE-2021-1328
📋 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 need valid administrator credentials to exploit improper input validation in the web management interface. 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 and potential lateral movement into connected networks.
Likely Case
Denial of service through device reboots, disrupting network connectivity for connected users and services.
If Mitigated
No impact if strong authentication controls prevent unauthorized access to admin credentials.
🎯 Exploit Status
Requires valid administrator credentials. Exploitation involves sending crafted HTTP requests to specific endpoints.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: RV016: 4.2.3.14, RV042/RV042G: 4.2.3.14, RV082: 4.2.3.14, RV320/RV325: 1.5.1.11
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 website. 4. Upload and install firmware. 5. Router will reboot automatically.
🔧 Temporary Workarounds
Disable Web Management Interface
allDisable the web-based management interface if not required, using CLI or alternative management methods.
no ip http server
no ip http secure-server
Restrict Management Access
allLimit web interface access to specific trusted IP addresses using access control lists.
access-list 1 permit 192.168.1.0 0.0.0.255
ip http access-class 1
🧯 If You Can't Patch
- Implement strong password policies and multi-factor authentication for admin accounts
- Isolate router management interfaces on separate VLAN with strict network segmentation
🔍 How to Verify
Check if Vulnerable:
Check current firmware version in web interface under Status > Router or via CLI command 'show version'Check Version:
show versionVerify Fix Applied:
Confirm firmware version matches or exceeds patched versions: RV016/RV042/RV042G/RV082 >= 4.2.3.14, RV320/RV325 >= 1.5.1.11📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by successful login
- Unusual HTTP POST requests to management endpoints
- Router reboot events in system logs
Network Indicators:
- Unusual HTTP traffic patterns to router management interface
- Multiple crafted HTTP requests from single source
SIEM Query:
source="router_logs" AND (event_type="authentication" AND result="success") FOLLOWED BY event_type="http_request" AND uri CONTAINS "/admin/" WITHIN 5 minutes