CVE-2020-8349
📋 TL;DR
This vulnerability allows unauthenticated remote code execution on Lenovo Cloud Networking Operating System (CNOS) devices when the optional REST API management interface is enabled and attached to a VRF. Only systems with the REST API interface enabled are affected, which is disabled by default. Attackers could potentially take full control of vulnerable networking devices.
💻 Affected Systems
- Lenovo Cloud Networking Operating System (CNOS)
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of networking infrastructure, allowing attackers to execute arbitrary code, pivot to other systems, disrupt network operations, and potentially access sensitive data.
Likely Case
Unauthorized access to network devices, configuration changes, service disruption, and potential lateral movement within the network.
If Mitigated
Limited or no impact if REST API interface is disabled or properly secured with VRF isolation and ACL restrictions.
🎯 Exploit Status
Vulnerability allows unauthenticated RCE, making exploitation straightforward if the REST API interface is accessible.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Non-vulnerable CNOS release (specific version not provided in advisory)
Vendor Advisory: https://support.lenovo.com/us/en/product_security/LEN-44423
Restart Required: Yes
Instructions:
1. Check current CNOS version. 2. Download and install latest non-vulnerable CNOS release from Lenovo support site. 3. Reboot device to apply update. 4. Verify update was successful.
🔧 Temporary Workarounds
Disable REST API Interface
allCompletely disable the vulnerable REST API management interface
no rest api enable
Restrict Access with VRF and ACL
allLimit REST API interface to management VRF and restrict access via ACLs
vrf management
ip access-list standard REST-API-ACL
permit host <authorized_ip>
deny any
interface <management_interface>
ip access-group REST-API-ACL in
🧯 If You Can't Patch
- Immediately disable the REST API management interface if not required
- Implement strict network segmentation, isolate management interfaces, and restrict access via ACLs to authorized management stations only
🔍 How to Verify
Check if Vulnerable:
Check if REST API interface is enabled: 'show running-config | include rest api enable'Check Version:
show versionVerify Fix Applied:
Verify CNOS version is updated to non-vulnerable release and REST API interface is either disabled or properly secured📡 Detection & Monitoring
Log Indicators:
- Unauthorized access attempts to REST API interface
- Unexpected configuration changes
- Unusual process execution
Network Indicators:
- Unusual traffic to REST API ports (typically 80/443)
- Traffic from unauthorized sources to management interfaces
SIEM Query:
source_ip NOT IN authorized_management_ips AND dest_port IN (80,443) AND dest_ip IN (cnos_devices)