CVE-2021-1159
📋 TL;DR
This vulnerability allows authenticated attackers with administrator credentials to execute arbitrary code as root or cause denial of service on affected Cisco Small Business routers. It affects RV110W, RV130, RV130W, and RV215W routers through improper input validation in the web management interface. Attackers can exploit it by sending crafted HTTP requests to vulnerable devices.
💻 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 full control of the router, network traffic interception, and persistence.
Likely Case
Denial of service through device reboots or targeted attacks by malicious insiders with admin access.
If Mitigated
Limited impact if strong access controls, network segmentation, and monitoring are in place to detect suspicious admin activity.
🎯 Exploit Status
Exploitation requires admin credentials but involves simple HTTP request crafting. No public exploit code 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 replacement.
🔧 Temporary Workarounds
Disable Web Management Interface
allDisable the vulnerable web interface and use alternative management methods like CLI or console.
Configure via CLI: no ip http server
no ip http secure-server
Restrict Management Access
allLimit web interface access to specific trusted IP addresses using access control lists.
ip http access-class <ACL-NUMBER>
ip http secure-server access-class <ACL-NUMBER>
🧯 If You Can't Patch
- Replace affected routers with supported models that receive security updates.
- Implement strict 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 command 'show version'. If model matches affected list and no patch exists, device is vulnerable.Check Version:
show versionVerify Fix Applied:
Verify web interface is disabled (CLI: 'show running-config | include http') or access is restricted via ACLs.📡 Detection & Monitoring
Log Indicators:
- Unusual HTTP POST requests to management interface
- Multiple authentication attempts followed by crafted requests
- Device reboot logs without clear cause
Network Indicators:
- HTTP traffic to router management port with unusual payload patterns
- Traffic from unexpected sources to admin interface
SIEM Query:
source="router_logs" AND (http_method="POST" AND uri="/admin/*" AND size>1000) OR (event="reboot" AND user="admin")