CVE-2021-1161
📋 TL;DR
Multiple input validation vulnerabilities in Cisco Small Business routers allow authenticated attackers to execute arbitrary code as root or cause denial of service. Attackers need valid administrator credentials to exploit these vulnerabilities. Affected devices include RV110W, RV130, RV130W, and RV215W routers.
💻 Affected Systems
- Cisco RV110W
- Cisco RV130
- Cisco RV130W
- Cisco RV215W
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise with root-level arbitrary code execution, allowing attacker to intercept traffic, modify configurations, or use device as pivot point into network.
Likely Case
Denial of service through device reboot, disrupting network connectivity for connected users and services.
If Mitigated
Limited to authenticated administrators only, reducing attack surface to credential compromise scenarios.
🎯 Exploit Status
Exploitation requires valid administrator credentials but involves simple HTTP request crafting once authenticated.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: N/A
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 vulnerable web-based management interface to prevent exploitation
Access router CLI via SSH/Telnet
Enter configuration mode
Disable HTTP/HTTPS management service
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 access management interface
🧯 If You Can't Patch
- Replace affected devices with supported models that receive security updates
- Implement network segmentation to isolate vulnerable routers from critical assets
🔍 How to Verify
Check if Vulnerable:
Check device model and firmware version against affected products list. All versions are vulnerable.Check Version:
show version (via CLI) or check web interface System Information pageVerify Fix Applied:
Verify web management interface is disabled or access is properly restricted via firewall rules.📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by successful login
- Unusual HTTP POST requests to management interface
- Device reboot logs without administrative action
Network Indicators:
- HTTP traffic to router management interface from unexpected sources
- Multiple authentication attempts from single source
SIEM Query:
source_ip="router_management_ip" AND (http_method="POST" OR status_code=200) AND user_agent NOT IN ["expected_browsers"]