How to remediate – Apache Default Index Page

1. Introduction

The Apache Default Index Page vulnerability occurs when a remote web server uses its default Apache index page. This can expose sensitive information, such as server root and installation paths, to attackers. It poses a medium risk to businesses by potentially allowing unauthorized access to system details. Systems commonly affected include those running the Apache HTTP Server with default configurations. A successful exploit could lead to information disclosure.

2. Technical Explanation

The vulnerability stems from using the default index page provided with Apache installations instead of a custom one. An attacker can simply request the default index page via HTTP or HTTPS to retrieve potentially sensitive data. No specific CVE exists for this general issue, but it is covered under OWASP guidelines. For example, an attacker could use a web browser to access http://example.com/index.html and view server information. Affected systems include Apache HTTP Server versions with default configurations enabled.

• Exploit mechanism: An attacker sends an HTTP request to access the default index page.
• Scope: Apache HTTP Server installations using default configuration files.

3. Detection and Assessment

To confirm vulnerability, first check if the default index page is accessible via a web browser. A thorough method involves inspecting the server’s response headers for clues about the Apache version and installed modules.

• Quick checks: Access http://example.com/index.html or http://example.com/index.htm in a web browser.
• Scanning: Nessus plugin ID 69435 can detect this issue, but results should be verified manually.
• Logs and evidence: Check Apache access logs for requests to the default index page files (e.g., /var/log/apache2/access.log).

curl -I http://example.com/index.html

4. Solution / Remediation Steps

Remove the default index page to mitigate this vulnerability. Follow these steps for a safe and effective fix.

4.1 Preparation

• Ensure you have access to modify the server’s file system. A roll back plan involves restoring the backed-up configuration files and restarting the service.
• A change window may be required for production systems; obtain approval from relevant stakeholders.

4.2 Implementation

1. Step 1: Delete or rename the default index page file (e.g., sudo rm /var/www/html/index.html).
2. Step 2: Create a custom index page, even if it’s just a simple “Under Construction” message.
3. Step 3: Restart the Apache service to apply the changes (e.g., sudo systemctl restart apache2).

4.3 Config or Code Example

Before

# Default Apache index page exists in /var/www/html/index.html

After

# No default index page present; custom index.html file created instead.

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent this type of vulnerability. Least privilege limits the impact if an attacker gains access. Safe defaults ensure systems are configured securely out-of-the-box. Regular patching keeps software up-to-date and protects against known vulnerabilities.

• Practice 1: Implement least privilege to reduce potential damage from information disclosure.
• Practice 2: Use safe defaults during server configuration, avoiding default settings where possible.

4.5 Automation (Optional)

#!/bin/bash
# Script to remove default Apache index page
if [ -f /var/www/html/index.html ]; then
  rm /var/www/html/index.html
  echo "Default index page removed."
fi
systemctl restart apache2

5. Verification / Validation

Confirm the fix by checking that the default index page is no longer accessible via a web browser. 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: Access http://example.com/index.html in a web browser; expect a “404 Not Found” error or your custom page.
• Re-test: Repeat the curl command from step 3 and verify that no default index page content is returned.
• Smoke test: Verify that other website pages are still accessible and functioning correctly.
• Monitoring: Monitor Apache access logs for any unexpected errors related to missing files.

curl -I http://example.com/index.html

6. Preventive Measures and Monitoring

Update security baselines to include the removal of default index pages. Implement checks in CI or deployment pipelines to prevent the same issue from recurring. Establish a regular patch review cycle to ensure timely updates.

• Baselines: Update your server hardening baseline to require custom index pages instead of defaults.
• Pipelines: Add a check during deployment to verify that no default index page files are present.
• Asset and patch process: Review Apache configuration changes as part of your regular security review cycle.

7. Risks, Side Effects, and Roll Back

• Risk or side effect 1: Potential disruption to services relying on the default index page; mitigate by creating a custom replacement.
• Risk or side effect 2: Incorrect configuration could lead to website errors; mitigate with thorough testing.
• Roll back: Restore backed-up Apache configuration files and restart the service (e.g., sudo systemctl restart apache2).

8. References and Resources

• Vendor advisory or bulletin: https://www.owasp.org/index.php/SCG_WS_Apache
• NVD or CVE entry: Not applicable for this general issue.
• Product or platform documentation relevant to the fix: https://httpd.apache.org/docs/2.4/