How to remediate – VMWare STARTTLS Support

1. Introduction

2. Technical Explanation

• Scope: VMWare products supporting STARTTLS are affected. Specific versions depend on the product; check vendor documentation.

3. Detection and Assessment

Confirming vulnerability involves checking if STARTTLS is supported on the VMWare server. A quick check can be done by attempting a connection with TLS enabled, then disabling it to see if the connection still succeeds. Thorough assessment requires examining the server configuration for STARTTLS settings.

• Quick checks: Use `openssl s_client -connect :` and check if TLS negotiation is successful. Then try without TLS.
• Scanning: Nessus plugin ID 16834 may identify STARTTLS support, but results should be verified manually.
• Logs and evidence: Examine VMWare server logs for messages related to TLS/STARTTLS negotiation. Specific log locations vary by product version.

openssl s_client -connect :443

4. Solution / Remediation Steps

4.1 Preparation

• Ensure you have access to the VMWare server configuration and understand how to modify it. A roll back plan is to restore from the snapshot.
• Changes should be approved by the security team or system owner.

4.2 Implementation

1. Step 1: Log in to the VMWare server administration interface.
2. Step 2: Locate the TLS/SSL configuration settings.
3. Step 3: Disable STARTTLS support if possible.
4. Step 4: If disabling is not an option, configure the server to require TLS for all connections.
5. Step 5: Restart the affected VMWare services to apply the changes.

4.3 Config or Code Example

Before

# STARTTLS enabled (example config)
ssl.enabled = true
starttls.enabled = true

After

# STARTTLS disabled, TLS required (example config)
ssl.enabled = true
starttls.enabled = false
require_tls = true

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent this type of issue. Least privilege reduces the impact if an attacker gains access. Secure defaults ensure encryption is enabled by default. A patch cadence ensures timely updates and fixes for known vulnerabilities.

• Practice 1: Least privilege limits the damage from compromised credentials.
• Practice 2: Secure defaults should require TLS/SSL for all connections.

4.5 Automation (Optional)

If using configuration management tools, automate the disabling of STARTTLS or enforcement of TLS. Be cautious when modifying server configurations remotely.

# Example Ansible task to disable STARTTLS
- name: Disable STARTTLS on VMWare Server
  lineinfile:
    path: /path/to/vmware_config.conf
    regexp: '^starttls.enabled = true$'
    line: 'starttls.enabled = false'
  notify: Restart VMware Service

5. Verification / Validation

Confirm the fix by checking that STARTTLS is disabled and TLS is required for all connections. Re-run the earlier detection method to verify the issue is resolved. Perform a basic service smoke test to ensure functionality remains intact.

• Post-fix check: Use `openssl s_client -connect :443` and confirm TLS negotiation succeeds, but attempts without TLS fail.
• Re-test: Repeat the quick check from section 3; STARTTLS should no longer be supported.
• Smoke test: Verify you can still log in to the VMWare server administration interface using a web browser.
• Monitoring: Monitor VMWare logs for TLS connection errors, which could indicate a regression.

openssl s_client -connect :443

6. Preventive Measures and Monitoring

Update security baselines to require TLS/SSL for all VMWare connections. Include checks in your CI/CD pipelines to prevent insecure configurations from being deployed. Implement a regular patch review cycle to address known vulnerabilities.

• Baselines: Update the server baseline or policy to enforce TLS encryption.
• Pipelines: Add configuration scanning tools to identify STARTTLS enabled services.
• Asset and patch process: Review security advisories weekly for VMWare products.

7. Risks, Side Effects, and Roll Back

Disabling STARTTLS may break compatibility with older clients that do not support TLS. Service interruption is possible if the configuration is incorrect. To roll back, restore from the snapshot taken in section 4.1.

• Risk or side effect 2: Incorrect configuration could lead to service interruption.
• Roll back:
  1. Step 1: Stop the affected VMWare services.
  2. Step 3: Restart the VMWare services.

8. References and Resources

• Vendor advisory or bulletin: VMWare Security Advisories
• NVD or CVE entry: No specific CVE currently exists for this configuration issue.
• Product or platform documentation relevant to the fix: VMWare Documentation