CVE-2021-26681
📋 TL;DR
This CVE describes a remote authenticated command injection vulnerability in Aruba ClearPass Policy Manager. Authenticated attackers can execute arbitrary commands as root on the underlying host, leading to complete system compromise. Affected versions include ClearPass Policy Manager prior to 6.9.5, 6.8.8-HF1, and 6.7.14-HF1.
💻 Affected Systems
- Aruba ClearPass Policy Manager
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with root-level access, allowing attackers to steal sensitive data, deploy malware, pivot to other systems, or disrupt operations.
Likely Case
Attackers with valid credentials gain full control of the ClearPass server, potentially compromising network authentication and policy enforcement.
If Mitigated
Limited impact if proper network segmentation, credential protection, and monitoring are in place to detect and block exploitation attempts.
🎯 Exploit Status
Exploitation requires authenticated access, but once obtained, command injection is straightforward. No public proof-of-concept has been disclosed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 6.9.5, 6.8.8-HF1, or 6.7.14-HF1
Vendor Advisory: https://www.arubanetworks.com/assets/alert/ARUBA-PSA-2021-004.txt
Restart Required: Yes
Instructions:
1. Backup ClearPass configuration and data. 2. Download the patched version from Aruba support portal. 3. Apply the update via the ClearPass admin interface or CLI. 4. Restart the ClearPass services or server as required.
🔧 Temporary Workarounds
Restrict CLI Access
allLimit access to the ClearPass CLI to trusted administrators only using network controls and strong authentication.
Monitor and Audit CLI Usage
allEnable logging for CLI commands and monitor for suspicious activity or unauthorized access attempts.
🧯 If You Can't Patch
- Implement strict access controls to limit who can authenticate to ClearPass, using multi-factor authentication if possible.
- Segment the ClearPass server network to restrict inbound and outbound traffic, reducing attack surface and lateral movement potential.
🔍 How to Verify
Check if Vulnerable:
Check the ClearPass version via the admin interface or CLI; if it's prior to 6.9.5, 6.8.8-HF1, or 6.7.14-HF1, it is vulnerable.Check Version:
In ClearPass CLI: 'show version' or via admin interface under System > About.Verify Fix Applied:
After patching, verify the version is 6.9.5, 6.8.8-HF1, or 6.7.14-HF1 or later, and test CLI functionality to ensure no regression.📡 Detection & Monitoring
Log Indicators:
- Unusual CLI command executions, especially with shell metacharacters or unexpected arguments.
- Failed authentication attempts followed by successful logins and command execution.
Network Indicators:
- Suspicious outbound connections from the ClearPass server to unknown IPs or ports, indicating potential command and control.
SIEM Query:
Example: 'source="clearpass" AND (event_type="cli_command" AND command CONTAINS "|" OR command CONTAINS ";")'