CVE-2017-3882
📋 TL;DR
A buffer overflow vulnerability in the UPnP implementation of Cisco CVR100W routers allows unauthenticated attackers on the same network segment to execute arbitrary code with root privileges or cause denial of service. This affects all firmware versions prior to 1.0.1.22, putting affected routers at high risk of complete compromise.
💻 Affected Systems
- Cisco CVR100W Wireless-N VPN Router
📦 What is this software?
Small Business Rv Router Firmware by Cisco
Small Business Rv Router Firmware by Cisco
Small Business Rv Router Firmware by Cisco
Small Business Rv Router Firmware by Cisco
Small Business Rv Router Firmware by Cisco
Small Business Rv Router Firmware by Cisco
Small Business Rv Router Firmware by Cisco
Small Business Rv Router Firmware by Cisco
Small Business Rv Router Firmware by Cisco
Small Business Rv Router Firmware by Cisco
Small Business Rv Router Firmware by Cisco
Small Business Rv Router Firmware by Cisco
Small Business Rv Router Firmware by Cisco
Small Business Rv Router Firmware by Cisco
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with root-level remote code execution, allowing attacker to install persistent backdoors, intercept all network traffic, or use the router as a pivot point into the network.
Likely Case
Denial of service causing router reboot and network disruption, with potential for subsequent exploitation attempts once the device is vulnerable again.
If Mitigated
Limited to denial of service if exploit attempts are blocked at network boundaries, though local network attackers could still potentially exploit.
🎯 Exploit Status
Exploitation requires sending malicious UPnP requests to port 1900/udp. Public exploit code exists and is relatively simple to execute.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firmware Release 1.0.1.22 or later
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170503-cvr100w1
Restart Required: Yes
Instructions:
1. Download firmware 1.0.1.22 or later from Cisco's support site. 2. Log into router web interface. 3. Navigate to Administration > Firmware Upgrade. 4. Upload and install the new firmware. 5. Router will reboot automatically.
🔧 Temporary Workarounds
Disable UPnP
allTurn off Universal Plug-and-Play service to prevent exploitation via this vector
Log into router web interface > Administration > Management > UPnP > Disable
Network Segmentation
allIsolate router management interface from user networks
Configure VLANs to separate management traffic from user traffic
🧯 If You Can't Patch
- Replace affected routers with supported models that receive security updates
- Implement strict network access controls to limit Layer 2 adjacency to trusted devices only
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router web interface under Status > Router > Firmware VersionCheck Version:
Check via web interface or SSH: show versionVerify Fix Applied:
Confirm firmware version is 1.0.1.22 or higher after upgrade📡 Detection & Monitoring
Log Indicators:
- Multiple malformed UPnP requests to port 1900
- Router reboot events without administrative action
- Unusual processes running on router
Network Indicators:
- Excessive UPnP traffic to router from single source
- Malformed UPnP packets containing shellcode patterns
SIEM Query:
source_port:1900 AND (packet_size:>1000 OR contains:"malformed")🔗 References
- http://www.securityfocus.com/bid/98287
- http://www.securitytracker.com/id/1038391
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170503-cvr100w1
- http://www.securityfocus.com/bid/98287
- http://www.securitytracker.com/id/1038391
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170503-cvr100w1
