CVE-2021-1177
📋 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 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 leading to complete device takeover, data exfiltration, and lateral movement into connected networks.
Likely Case
Denial of service through device reboots disrupting network connectivity and business operations.
If Mitigated
Limited impact if strong authentication controls prevent unauthorized access to admin credentials.
🎯 Exploit Status
Requires valid administrator credentials but exploitation is straightforward 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 and use alternative management methods
Access router CLI via SSH/Telnet
Enter configuration mode: 'configure terminal'
Disable HTTP server: 'no ip http server'
Disable HTTPS server: 'no ip http secure-server'
Save configuration: 'write memory'
Restrict Management Access
allLimit web management interface access to specific trusted IP addresses only
Access router CLI via SSH/Telnet
Enter configuration mode: 'configure terminal'
Create ACL: 'access-list 10 permit [trusted-ip]'
Apply to HTTP: 'ip http access-class 10'
Apply to HTTPS: 'ip http secure-server access-class 10'
Save configuration: 'write memory'
🧯 If You Can't Patch
- Replace affected routers with supported models that receive security updates
- Implement network segmentation to isolate routers from critical systems
🔍 How to Verify
Check if Vulnerable:
Check router model and firmware version via web interface or CLI command 'show version'Check Version:
show version | include SoftwareVerify Fix Applied:
Verify web management interface is disabled: 'show running-config | include http' should show no http/https servers enabled📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by successful login
- Unusual HTTP POST requests to management interface
- Device reboot logs without scheduled maintenance
Network Indicators:
- Unusual outbound connections from router to external IPs
- HTTP traffic patterns matching exploit payloads
SIEM Query:
source="router_logs" (event_type="authentication" AND result="success") AND (http_method="POST" AND uri="/admin/*")