How to remediate – ZEN Load Balancer global.conf Information Disclosure

1. Introduction

ZEN Load Balancer global.conf Information Disclosure is a vulnerability where sensitive configuration data can be accessed without permission. This allows attackers to learn details about your web application, potentially leading to further attacks. Web servers using ZEN Load Balancer are usually affected. A successful exploit could compromise the confidentiality of application settings and credentials.

2. Technical Explanation

The version of ZEN Load Balancer hosted on a remote server does not properly restrict access to its ‘config/global.conf’ file. This allows anyone to view this file over the web. An attacker can simply request the file and read its contents.

• Root cause: Missing access controls on the ‘config/global.conf’ file.
• Exploit mechanism: An attacker sends an HTTP GET request to the vulnerable URL, for example http://example.com/config/global.conf.
• Scope: ZEN Load Balancer versions are affected; specific versions were not provided in the context.

3. Detection and Assessment

You can check if your system is vulnerable by attempting to access the configuration file directly. More thorough scanning tools can also identify this issue.

• Quick checks: Use a web browser or curl to request http://your-load-balancer-ip/config/global.conf. If you see configuration data, your system is vulnerable.
• Scanning: Nessus ID 779315ef may detect this vulnerability as an example.
• Logs and evidence: Check web server access logs for requests to ‘/config/global.conf’.

curl http://your-load-balancer-ip/config/global.conf

4. Solution / Remediation Steps

Currently, there is no official solution available from the vendor. Mitigation focuses on restricting access to the configuration file.

4.1 Preparation

• Dependencies: Access to the web server’s configuration files. Roll back involves restoring the original configuration if needed.
• Change window needs: Standard change control processes should be followed.

4.2 Implementation

1. Step 1: Configure your web server (e.g., Apache, Nginx) to deny access to ‘/config/global.conf’.
2. Step 2: Restart the web server to apply the changes.

4.3 Config or Code Example

Before

# No specific configuration blocking access to /config/global.conf

After

<Location /config/global.conf>
  Order deny,allow
  Deny from all
</Location>

4.4 Security Practices Relevant to This Vulnerability

Least privilege and secure defaults are important practices for preventing this issue. Regularly review configurations for unnecessary exposure of sensitive data.

• Practice 1: Least privilege – restrict access to configuration files to only those users who need it.
• Practice 2: Secure defaults – configure systems with the most restrictive settings possible by default.

4.5 Automation (Optional)

If you manage your web server configurations using infrastructure-as-code, automate the addition of access restrictions to ‘/config/global.conf’.

# Example Ansible task
- name: Block access to global.conf
  lineinfile:
    path: /etc/apache2/sites-available/your_site.conf # Adjust path as needed
    regexp: '^<Location /config/global.conf>'
    insertbefore: '^</VirtualHost>'
    state: present
    line: '<Location /config/global.conf>n  Order deny,allown  Deny from alln</Location>'

5. Verification / Validation

• Post-fix check: Use a web browser or curl to request http://your-load-balancer-ip/config/global.conf. You should receive a ‘403 Forbidden’ error.
• Re-test: Repeat the quick check from section 3; you should no longer be able to access the file.
• Monitoring: Check web server logs for any failed attempts to access ‘/config/global.conf’.

curl -I http://your-load-balancer-ip/config/global.conf

6. Preventive Measures and Monitoring

Update security baselines to include restrictions on sensitive configuration files. Implement regular vulnerability scanning in your CI pipelines.

• Baselines: Update a security baseline or policy to require access controls on all configuration files.
• Pipelines: Add checks in CI/CD pipelines to scan for publicly accessible configuration files.
• Asset and patch process: Review configurations regularly as part of your asset management process.

7. Risks, Side Effects, and Roll Back

• Risk or side effect 1: Incorrect configuration could cause web server errors; review logs carefully.
• Roll back: Restore the original web server configuration file if issues occur. Restart the web server to apply the changes.

8. References and Resources

• Vendor advisory or bulletin: No vendor advisory was provided in the context.
• NVD or CVE entry: No CVE was provided in the context.
• Product or platform documentation relevant to the fix: http://www.nessus.org/u?779315ef