CVE-2021-1204
📋 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 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 device.
If Mitigated
No impact if proper network segmentation, credential management, and access controls prevent attackers from reaching the management interface.
🎯 Exploit Status
Exploitation requires valid admin credentials but involves simple HTTP request crafting. No public exploit code is confirmed.
🛠️ 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. Cisco has not released updates. Consider workarounds or device 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
Configure no ip http server
Configure no ip http secure-server
Restrict Management Access
allLimit web management interface access to specific trusted IP addresses only
Configure ip http access-class [ACL-NAME]
Create ACL permitting only trusted management stations
🧯 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-restricted via 'show running-config | include http'📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by successful login
- Unusual HTTP POST requests to management endpoints
- Device reboot logs without scheduled maintenance
Network Indicators:
- HTTP traffic to router management interface from unexpected sources
- Unusual outbound connections from router after management interface access
SIEM Query:
source="router_logs" (event_type="authentication" AND result="success") AND (src_ip NOT IN [trusted_management_ips])