How to remediate – XMPP Server Detection

1. Introduction

An XMPP Server Detection indicates an instant messaging server supporting the Extensible Messaging and Presence Protocol is running on a remote host. This matters because open messaging servers can be exploited for unauthorised access to communications, data breaches, and denial of service attacks. Systems commonly affected include those hosting internal communication platforms or inadvertently running XMPP services. A successful exploit could compromise confidentiality, integrity, and availability of the server and connected systems.

2. Technical Explanation

An XMPP server is listening on a network port, allowing connections from clients using the XMPP protocol. This isn’t necessarily an error but indicates a service that needs review against security policy. Exploitation typically involves gaining unauthorised access to the server and then intercepting or manipulating messages. Preconditions include network connectivity to the server’s port and valid credentials if authentication is required.

• Root cause: The XMPP service is enabled and accessible on the network.
• Exploit mechanism: An attacker connects to the XMPP server, authenticates (if necessary), and then uses protocol features to access messages or control connected clients.
• Scope: Any system running an XMPP server software package, such as ejabberd, Openfire, or similar.

3. Detection and Assessment

Confirming the presence of an XMPP server can be done with network scanning tools or by checking listening ports on a host. Thorough assessment involves examining the server’s configuration for security weaknesses.

• Quick checks: Use netstat -tulnp to list listening ports and identify processes associated with XMPP (e.g., java, ejabberd).
• Scanning: Nessus plugin ID 34850 can detect open XMPP ports. This is an example only.
• Logs and evidence: Check system logs for messages related to the XMPP server startup or client connections. Look in /var/log/ejabberd/*.log if using ejabberd.

netstat -tulnp | grep 5222

4. Solution / Remediation Steps

The following steps outline how to address an XMPP server detection. Ensure the service is required and configured securely.

4.1 Preparation

• Ensure you have access to restart the service or restore from the snapshot. A roll back plan is to revert to the previous snapshot.
• Changes should be made during a scheduled maintenance window with appropriate approval.

4.2 Implementation

1. Step 1: Review your corporate security policy regarding instant messaging services.
2. Step 2: If the service is not required, disable it using the system’s service manager (e.g., systemctl stop ejabberd).
3. Step 3: If the service is required, limit incoming traffic to the XMPP port (typically 5222) using a firewall.
4. Step 4: Configure strong authentication for all users of the XMPP server.

4.3 Config or Code Example

Before

# /etc/ejabberd.yml (example)
listen:
  - {port: 5222, domain: example.com}

After

# /etc/ejabberd.yml (example)
listen:
  - {port: 5222, domain: example.com, access: allowed_ips}
access:
  allowed_ips:
    - 192.168.1.0/24 # Example trusted network

4.4 Security Practices Relevant to This Vulnerability

Several security practices can mitigate the risks associated with running an XMPP server.

• Practice 1: Least privilege – restrict access to the XMPP server and its data to only authorised users.
• Practice 2: Network segmentation – isolate the XMPP server on a separate network segment to limit the impact of a compromise.

4.5 Automation (Optional)

If using infrastructure as code, you can automate firewall rule updates.

# Example Ansible snippet
- name: Allow XMPP traffic from trusted networks
  firewalld:
    port: 5222/tcp
    permanent: true
    state: enabled
    zone: internal
    source: 192.168.1.0/24 # Example trusted network

5. Verification / Validation

Confirm the fix by checking that traffic is restricted as expected and the service remains functional for authorised users.

• Post-fix check: Run netstat -tulnp | grep 5222 to confirm the XMPP server is still listening.
• Re-test: Re-run the initial scan (e.g., Nessus plugin ID 34850) and verify it no longer reports an open, unrestricted port.
• Smoke test: Verify that authorised users can connect to the XMPP server and send/receive messages.
• Monitoring: Check firewall logs for blocked connections to port 5222 from untrusted sources. This is an example only.

netstat -tulnp | grep 5222

6. Preventive Measures and Monitoring

Regular security assessments and policy enforcement can prevent similar issues.

• Baselines: Update your network baseline to include expected services and ports, flagging any deviations.
• Pipelines: Include port scanning in CI/CD pipelines to identify unexpected open ports during deployment.
• Asset and patch process: Review the asset inventory regularly to ensure all running software is known and managed.

7. Risks, Side Effects, and Roll Back

Disabling or restricting access to the XMPP server may impact users who rely on it for communication.

• Risk or side effect 1: Service disruption – disabling the service will prevent users from sending/receiving messages.
• Risk or side effect 2: Connectivity issues – incorrect firewall rules can block legitimate traffic.
• Roll back: Step 1: Re-enable the XMPP service (e.g., systemctl start ejabberd). Step 2: Restore the original firewall configuration. Step 3: Verify that users can connect to the server.

8. References and Resources

Links related to this specific vulnerability.

• Vendor advisory or bulletin: https://xmpp.org/rfcs/rfc3920.html