CVE-2021-1187
📋 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 Router
- Cisco Small Business RV130 Router
- Cisco Small Business RV130W Router
- Cisco Small Business RV215W Router
📦 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
Exploitation requires valid admin credentials but involves simple HTTP request crafting once credentials are obtained.
🛠️ 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. Consider workarounds or replacement.
🔧 Temporary Workarounds
Disable Web Management Interface
allDisable the vulnerable web-based management interface and use alternative management methods
Access router CLI via SSH/Telnet
Navigate to web management settings
Disable HTTP/HTTPS management interface
Restrict Management Access
allLimit web management interface access to specific trusted IP addresses only
Configure firewall rules to restrict access to router management IP
Allow only specific source IPs to connect to management ports
🧯 If You Can't Patch
- Replace affected routers with supported models that receive security updates
- Implement network segmentation to isolate vulnerable routers from critical assets
🔍 How to Verify
Check if Vulnerable:
Check router model and firmware version via web interface or CLI. If model is RV110W, RV130, RV130W, or RV215W, device is vulnerable.Check Version:
show version (via CLI) or check System Information in web interfaceVerify Fix Applied:
No fix available to verify. Verify workarounds by testing that web interface is inaccessible or restricted.📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by successful login
- Unusual HTTP requests to management interface
- Device reboot logs without normal cause
Network Indicators:
- HTTP requests with crafted/malformed parameters to router management IP
- Traffic from unexpected sources to router management ports
SIEM Query:
source_ip="router_management_ip" AND (http_method="POST" OR http_method="GET") AND (url_contains("cgi-bin") OR parameter_contains("crafted"))