1. Introduction
The Apache HTTP Server Site Enumeration vulnerability allows attackers to retrieve domain names and IP addresses from an Apache HTTP Server’s configuration file. This information can be used for reconnaissance, mapping attack surfaces, and identifying potential targets. The vulnerability primarily affects Linux- and Unix-based systems running the Apache HTTP Server webserver. A successful exploit could lead to information disclosure, potentially impacting confidentiality.
2. Technical Explanation
The vulnerability occurs because Apache HTTP Server may expose its configuration file containing domain names and IP addresses. An attacker can directly request this file from a vulnerable server. There is no known CVE associated with this specific enumeration issue; however, it relates to the overall security of Apache HTTP Server configurations. For example, an attacker could use a simple HTTP GET request to retrieve the sensitive information.
- Root cause: The Apache configuration file contains domain names and IP addresses that are accessible via HTTP requests.
- Exploit mechanism: An attacker sends an HTTP GET request to the server attempting to access the configuration file directly.
- Scope: Linux- and Unix-based hosts running Apache HTTP Server are affected.
3. Detection and Assessment
You can confirm a system is vulnerable by checking for accessible configuration files. A thorough method involves reviewing the server’s webserver configuration.
- Quick checks: Use `curl -I
/apache2/conf/httpd.conf` or similar to check if the configuration file is directly accessible. - Scanning: Nessus plugin ID 16384 can identify Apache HTTP Server Site Enumeration. This is an example only, and results should be verified manually.
- Logs and evidence: Check web server access logs for requests targeting common configuration file paths (e.g., /apache2/conf/httpd.conf).
curl -I http://example.com/apache2/conf/httpd.conf4. Solution / Remediation Steps
The following steps provide a precise method to fix the issue.
4.1 Preparation
- Ensure you have access to the server’s configuration files and appropriate permissions. A roll back plan involves restoring the backed-up configuration files.
- A change window may be required depending on your environment, and approval from system administrators is recommended.
4.2 Implementation
- Step 1: Edit the Apache HTTP Server main configuration file (e.g., /etc/apache2/apache2.conf or /etc/httpd/conf/httpd.conf).
- Step 2: Ensure that directory listing is disabled for the directories containing sensitive configuration files. Add `
Options -Indexes ` to your config file. Repeat this step for any other relevant directories. - Step 3: Restart the Apache service using `sudo systemctl restart apache2` or equivalent command for your distribution.
4.3 Config or Code Example
Before
<Directory "/etc/apache2">
Options Indexes FollowSymLinks
AllowOverride None
Require all granted
</Directory>After
<Directory "/etc/apache2">
Options -Indexes FollowSymLinks
AllowOverride None
Require all granted
</Directory>4.4 Security Practices Relevant to This Vulnerability
Several security practices can help prevent this issue.
- Practice 1: Least privilege – restrict access to configuration files to only authorized users and processes.
- Practice 2: Secure defaults – configure Apache with secure settings by default, disabling directory listing for sensitive directories.
4.5 Automation (Optional)
No automation script is provided as this fix requires careful consideration of the server environment. Incorrect configuration can lead to service disruption.
5. Verification / Validation
Confirm the fix by checking that the configuration file is no longer accessible via HTTP.
- Post-fix check: Run `curl -I
/apache2/conf/httpd.conf`. The expected output should be a 403 Forbidden error or similar access denied message. - Re-test: Re-run the quick check from Section 3 to confirm that the configuration file is no longer accessible.
- Monitoring: Monitor web server access logs for any attempts to access sensitive configuration files.
curl -I http://example.com/apache2/conf/httpd.conf6. Preventive Measures and Monitoring
Update security baselines and implement checks in your CI/CD pipelines.
- Baselines: Update your server security baseline to include the configuration changes described above, such as disabling directory listing for sensitive directories.
- Asset and patch process: Implement a regular review cycle for Apache configurations to ensure they remain secure.
7. Risks, Side Effects, and Roll Back
Incorrect configuration changes may lead to service disruption.
- Roll back: Restore the backed-up Apache configuration files and restart the service.
8. References and Resources
Link only to sources that match this exact vulnerability.
- Vendor advisory or bulletin: https://httpd.apache.org/