CVE-2021-1173
📋 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 these specific router models 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
Full system compromise with root-level arbitrary code execution, allowing complete device takeover, data exfiltration, 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.
If Mitigated
No impact if proper credential management prevents unauthorized administrative access.
🎯 Exploit Status
Exploitation requires authenticated access 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. 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
Configure using 'no ip http server' or equivalent
Use alternative management methods
Restrict Management Access
allLimit web management interface access to trusted IP addresses only
Configure ACLs to restrict HTTP/HTTPS access
Implement management VLAN segregation
Use VPN for remote management
🧯 If You Can't Patch
- Replace affected routers with supported models that receive security updates
- Implement network segmentation to isolate routers from critical assets
🔍 How to Verify
Check if Vulnerable:
Check router 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 ACLs.📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by successful login
- Unusual HTTP requests to management interface
- Device reboot logs without scheduled maintenance
Network Indicators:
- HTTP traffic to router management interface from unexpected sources
- Unusual outbound connections from router after management access
SIEM Query:
source_ip="router_management_ip" AND (http_method="POST" OR http_method="GET") AND uri_contains("/admin/") AND status_code=200