CVE-2021-1196
📋 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. It affects users of RV110W, RV130, RV130W, and RV215W routers with web-based management enabled. Attackers need valid administrator credentials to exploit it.
💻 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
Full system compromise with root-level arbitrary code execution, leading to data theft, network manipulation, or persistent backdoor installation.
Likely Case
Denial of service from device reboots or targeted attacks by malicious insiders or credential-stealing attackers.
If Mitigated
Limited impact if strong access controls, network segmentation, and monitoring are in place to restrict admin access.
🎯 Exploit Status
Exploitation requires authenticated access; complexity is low due to improper input validation in the web interface.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: None
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-rv-overflow-WUnUgv4U
Restart Required: No
Instructions:
No official patch available; follow workarounds or mitigation steps.
🔧 Temporary Workarounds
Disable Web-Based Management Interface
allTurn off the web management interface to prevent HTTP-based exploitation.
Access router CLI via SSH or console, then use commands like 'no ip http server' or disable via web GUI if possible.
Restrict Access to Management Interface
allLimit access to the web interface using firewall rules or ACLs to trusted IPs only.
Configure firewall on router to allow only specific IPs to port 80/443, e.g., 'access-list 1 permit 192.168.1.0 0.0.0.255' and apply to interface.
🧯 If You Can't Patch
- Replace affected routers with supported models that receive security updates.
- Implement network segmentation to isolate routers and monitor for suspicious HTTP traffic.
🔍 How to Verify
Check if Vulnerable:
Check if you are using an affected router model and if web management is enabled; no specific command to test vulnerability safely.Check Version:
Log into router web interface or CLI and check firmware version in settings or use 'show version' command.Verify Fix Applied:
Verify workarounds by confirming web interface is disabled or access is restricted via firewall rules.📡 Detection & Monitoring
Log Indicators:
- Unusual HTTP requests to management interface, multiple failed login attempts followed by crafted requests, or device reboot logs.
Network Indicators:
- Suspicious HTTP traffic to router management ports (80/443) from unauthorized sources.
SIEM Query:
Example: 'source_ip=router_ip AND (http_method=POST OR http_method=GET) AND url_contains="/admin/" AND status_code=200'