CVE-2021-1185
📋 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, network traffic interception, and lateral movement into connected networks.
Likely Case
Authenticated attackers with admin credentials gaining persistent access to routers, potentially using them as footholds for further attacks or causing service disruption through device reboots.
If Mitigated
Limited impact if strong credential management and network segmentation prevent unauthorized access to admin interfaces.
🎯 Exploit Status
Exploitation requires valid admin credentials but involves simple HTTP request crafting once authenticated.
🛠️ 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
Use CLI: no ip http server
no ip http secure-server
Restrict Management Access
allLimit management interface access to specific trusted IP addresses only
ip http access-class [ACL-NAME]
ip http secure-server access-class [ACL-NAME]
🧯 If You Can't Patch
- Replace affected routers with supported models that receive security updates
- Implement strict network segmentation to isolate vulnerable routers from critical assets
🔍 How to Verify
Check if Vulnerable:
Check router model and firmware version against affected products list. Verify web management interface is enabled.Check Version:
show versionVerify Fix Applied:
Verify web management interface is disabled or access is restricted via ACLs. Test that HTTP/HTTPS management ports are not accessible.📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by successful login and unusual HTTP requests
- Device reboot logs without scheduled maintenance
- Unusual process execution or configuration changes
Network Indicators:
- Unusual HTTP traffic patterns to router management interface
- Traffic from unexpected sources to management ports (80, 443, 8080)
SIEM Query:
source="router_logs" (event="authentication success" AND event="configuration change" OR event="device reboot")