CVE-2021-1171
📋 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 these input validation flaws in the web management interface. Organizations using Cisco RV110W, RV130, RV130W, or RV215W routers are affected.
💻 Affected Systems
- Cisco Small Business RV110W
- Cisco Small Business RV130
- Cisco Small Business RV130W
- Cisco Small Business RV215W
📦 What is this software?
⚠️ 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
Limited impact if strong authentication controls prevent unauthorized access to admin credentials.
🎯 Exploit Status
Requires valid administrator credentials. Exploitation involves sending crafted HTTP requests to the web interface.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: None available
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-rv-overflow-WUnUgv4U
Restart Required: No
Instructions:
No official patch available. Cisco has not released software updates. Consider workarounds or replacement.
🔧 Temporary Workarounds
Disable web management interface
allDisable the web-based management interface and use alternative management methods like CLI or dedicated management networks
Restrict access to management interface
allImplement strict network access controls to limit which IP addresses can reach the web management interface
🧯 If You Can't Patch
- Replace affected routers with supported models that receive security updates
- Implement network segmentation to isolate affected routers from critical systems
🔍 How to Verify
Check if Vulnerable:
Check router model and firmware version via web interface or CLI. If using RV110W, RV130, RV130W, or RV215W, assume vulnerable.Check Version:
Login to web interface and check System Information, or use CLI command 'show version'Verify Fix Applied:
No fix available to verify. Verify workarounds by confirming web interface is disabled or access-restricted.📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by successful login
- Unusual HTTP requests to management interface endpoints
- Device reboot logs without scheduled maintenance
Network Indicators:
- HTTP traffic to router management interface from unusual sources
- Multiple HTTP POST requests with crafted payloads
SIEM Query:
source="router_logs" AND (event="authentication_success" AND user="admin" AND src_ip NOT IN [allowed_management_ips]) OR event="device_reboot"