CVE-2021-1192
📋 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 RV110W, RV130, RV130W, or RV215W routers are affected.
💻 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 persistent backdoor installation, network traffic interception, and lateral movement to connected systems.
Likely Case
Device reboot causing temporary service disruption, or limited code execution for reconnaissance and credential harvesting from the compromised router.
If Mitigated
No impact if proper network segmentation, credential management, and access controls prevent attackers from reaching the management interface.
🎯 Exploit Status
Requires valid admin credentials but uses simple HTTP request manipulation. Credential theft or weak passwords make exploitation trivial.
🛠️ 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 exists. Follow workarounds and consider hardware replacement.
🔧 Temporary Workarounds
Disable Web Management Interface
allCompletely disable the vulnerable web-based management interface and use CLI or other management methods.
no ip http server
no ip http secure-server
Restrict Management Access
allLimit management interface access to specific trusted IP addresses using ACLs.
ip http access-class MANAGEMENT-ACL
ip http secure-server access-class MANAGEMENT-ACL
🧯 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 via web interface or CLI 'show version' commandCheck Version:
show versionVerify Fix Applied:
Verify web interface is disabled or access is restricted via 'show running-config | include http'📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts followed by successful login and unusual HTTP POST requests to management endpoints
- Device reboot logs without scheduled maintenance
Network Indicators:
- Unusual outbound connections from router to external IPs
- HTTP traffic to router management interface from unexpected sources
SIEM Query:
source="router_logs" (event_type="authentication_success" AND src_ip NOT IN [trusted_management_ips]) OR (uri_path CONTAINS "/admin/" AND method="POST" AND size>normal)