How to remediate – Wireless Access Controller Detection

1. Introduction

A wireless access controller is listening on the remote host, indicating the Control And Provisioning of Wireless Access Points (CAPWAP) protocol is in use. CAPWAP allows a central controller to manage multiple wireless points. This can create an attack surface if not properly secured. A successful exploit could allow remote attackers to gain control of managed access points and potentially compromise the network. Confidentiality, integrity, and availability may be impacted.

2. Technical Explanation

The CAPWAP protocol enables communication between wireless controllers and access points. If a host is listening for CAPWAP traffic, it suggests an Access Controller service is running. Attackers can exploit this by attempting to connect as a rogue access point or intercepting communications. There are no known CVEs specifically targeting CAPWAP detection itself; the risk lies in misconfiguration of the AC and WTPs. An attacker could attempt to gain management access to wireless points, potentially altering configurations or capturing network traffic.

• Root cause: The presence of a listening CAPWAP service on a host indicates potential exposure.
• Exploit mechanism: Attackers can attempt to establish a CAPWAP connection and exploit vulnerabilities in the AC’s management interface.
• Scope: Wireless controllers from various vendors (e.g., Cisco, Aruba, Juniper) are affected if CAPWAP is enabled.

3. Detection and Assessment

Confirming a CAPWAP listener helps assess potential exposure. A quick check can identify the service; thorough methods involve packet capture analysis.

• Quick checks: Use netstat -tulnp to look for processes listening on UDP port 5246 (the default CAPWAP port).
• Scanning: Nmap with the script nmap --script capwap-discovery can identify CAPWAP services. This is an example only and may not be comprehensive.
• Logs and evidence: Check system logs for messages related to CAPWAP or wireless controller activity.

netstat -tulnp | grep 5246

4. Solution / Remediation Steps

Fixing this issue involves securing the Access Controller and limiting exposure. These steps should be performed during a maintenance window.

4.1 Preparation

• Ensure you have access to the Access Controller’s management interface and rollback plans are in place. A roll back plan is to restore from backup.
• A change window may be required, depending on your organisation’s policies. Approval from a senior network engineer might also be needed.

4.2 Implementation

1. Step 1: Change the default CAPWAP port (5246) to a non-standard value.
2. Step 2: Enable WPA3 encryption on all wireless networks managed by the controller.
3. Step 3: Implement access control lists (ACLs) to restrict CAPWAP traffic to only trusted IP addresses.

4.3 Config or Code Example

Before

interface wlan0
  capwap port 5246

After

interface wlan0
  capwap port 7890
  capwap acl trusted_ips

4.4 Security Practices Relevant to This Vulnerability

Several security practices can mitigate this risk. Least privilege limits the impact of a compromise, while input validation prevents malicious data from being processed.

• Practice 1: Implement least privilege access controls on the Access Controller management interface to reduce the potential damage if an attacker gains access.
• Practice 2: Use strong authentication methods (e.g., multi-factor authentication) for all Access Controller logins.

4.5 Automation (Optional)

# Example Ansible task to change CAPWAP port (use with caution)
- name: Change CAPWAP Port
  ansible.builtin.lineinfile:
    path: /etc/config/wireless_controller.conf
    regexp: 'capwap port 5246'
    line: 'capwap port 7890'
  become: true

5. Verification / Validation

Confirm the fix by verifying the CAPWAP port change and re-running detection methods. A service smoke test ensures functionality remains intact.

• Post-fix check: Run netstat -tulnp | grep 7890 (or your chosen new port) to confirm the service is listening on the correct port.
• Re-test: Re-run the Nmap scan from step 3 and verify that CAPWAP is no longer detected on port 5246.
• Monitoring: Monitor system logs for any errors related to CAPWAP or wireless controller activity.

netstat -tulnp | grep 7890

6. Preventive Measures and Monitoring

Update security baselines and implement checks in CI/CD pipelines to prevent similar issues. Regular patch reviews are also essential.

• Baselines: Update your wireless controller security baseline to include the recommended CAPWAP configuration settings (e.g., port change, ACLs).
• Pipelines: Add static analysis checks in your CI/CD pipeline to identify insecure configurations or default credentials in wireless controller configuration files.
• Asset and patch process: Implement a regular review cycle for wireless controller firmware updates and security patches.

7. Risks, Side Effects, and Roll Back

Changing the CAPWAP port may disrupt connectivity if not properly configured. Rolling back involves restoring the original configuration.

• Roll back: Restore the wireless controller configuration from the backup taken in step 1.

8. References and Resources

• Vendor advisory or bulletin: Check your wireless controller vendor’s website for specific security recommendations related to CAPWAP.
• NVD or CVE entry: No specific CVE exists for CAPWAP detection itself, but review relevant CVEs for the Access Controller software.
• Product or platform documentation relevant to the fix: Refer to your wireless controller’s configuration guide for details on changing the CAPWAP port and implementing ACLs.