CVE-2020-3171
📋 TL;DR
This vulnerability allows authenticated local attackers to execute arbitrary commands on Cisco FXOS and UCS Manager devices through the local management CLI. Attackers can exploit insufficient input validation by crafting malicious arguments to specific commands. Affected systems include Cisco FXOS Software and Cisco UCS Manager Software, with Cisco UCS 6400 Series Fabric Interconnects being particularly vulnerable as commands execute with root privileges.
💻 Affected Systems
- Cisco FXOS Software
- Cisco UCS Manager Software
📦 What is this software?
Fxos by Cisco
Fxos by Cisco
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with root-level access on UCS 6400 Series Fabric Interconnects, allowing full control over the device, data exfiltration, and lateral movement within the network.
Likely Case
Privilege escalation and execution of arbitrary commands with the privileges of the currently logged-in user, potentially leading to configuration changes, data access, and further exploitation.
If Mitigated
Limited impact if proper access controls restrict local management CLI access to trusted administrators only, reducing the attack surface.
🎯 Exploit Status
Exploitation requires authenticated local access to the CLI and knowledge of specific vulnerable commands. The vulnerability is due to insufficient input validation, making exploitation straightforward for attackers with the required access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Refer to Cisco Security Advisory for specific fixed versions for each product
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20200226-fxos-ucs-cli-cmdinj
Restart Required: Yes
Instructions:
1. Review Cisco Security Advisory for affected versions. 2. Download and apply the appropriate fixed software version for your device. 3. Reboot the device after patching. 4. Verify the patch is applied correctly.
🔧 Temporary Workarounds
Restrict Local Management CLI Access
allLimit access to the local management CLI to only trusted administrators using role-based access controls and strong authentication.
Monitor CLI Command Usage
allImplement logging and monitoring of CLI commands to detect suspicious activity and potential exploitation attempts.
🧯 If You Can't Patch
- Implement strict access controls to limit local CLI access to essential personnel only
- Enable comprehensive logging and monitoring of CLI sessions for anomalous command usage
🔍 How to Verify
Check if Vulnerable:
Check your device's software version against the affected versions listed in the Cisco Security Advisory.Check Version:
show version (on affected Cisco devices)Verify Fix Applied:
Verify the installed software version matches or exceeds the fixed versions specified in the Cisco Security Advisory.📡 Detection & Monitoring
Log Indicators:
- Unusual CLI command patterns
- Commands with unexpected arguments or syntax
- Multiple failed authentication attempts followed by successful login
Network Indicators:
- Unusual outbound connections from management interfaces
- Anomalous traffic patterns from affected devices
SIEM Query:
Search for CLI command logs containing suspicious arguments or patterns indicative of command injection attempts.