1. Introduction
The Web Server Office File Inventory vulnerability means your web server is hosting documents like Word files, spreadsheets and PDFs. This matters because these files could contain sensitive information that attackers might steal if they gain access. Systems running any web server software capable of serving static files are usually affected. A successful exploit could lead to confidential data being exposed, potentially impacting the integrity of your business processes and availability of services.
2. Technical Explanation
This vulnerability occurs when office-related files are stored on a publicly accessible web server without adequate protection. An attacker can directly request these files and download them if they know their location. There is no specific CVE associated with this general finding, but it falls under CWE-590: Insufficient Protection of Sensitive Information. For example, an attacker could simply browse the web server’s directory structure or use a tool like wget to enumerate and download all .doc files. Affected systems include any web server (Apache, Nginx, IIS) with publicly accessible file storage.
- Root cause: Files are stored on the webserver without appropriate access controls.
- Exploit mechanism: An attacker requests a file directly via HTTP or HTTPS.
- Scope: All web servers hosting office documents are potentially affected, regardless of operating system or specific software version.
3. Detection and Assessment
You can confirm this vulnerability by checking your web server’s directory structure for office files. A thorough assessment involves scanning the entire webserver file system.
- Quick checks: Use a web browser to navigate to common locations where files might be stored (e.g., /documents, /files).
- Scanning: Nessus plugin ID 10423 can identify office files on web servers as an example.
- Logs and evidence: Web server access logs may show requests for .doc, .ppt, .xls or .pdf files. Look for unusual download activity.
ls -l /var/www/html/documents | grep '.(doc|ppt|xls|pdf)'4. Solution / Remediation Steps
Fixing this issue requires ensuring sensitive files are protected or removed from the web server. Follow these steps to secure your system.
4.1 Preparation
- Ensure you have a list of all office files currently hosted on the server. A roll back plan involves restoring the backup if issues occur.
- A change window may be needed depending on your organisation’s policies and the size of the file system. Approval from the IT Security team might also be required.
4.2 Implementation
- Step 1: Identify all office files (.doc, .ppt, .xls, .pdf) stored in publicly accessible directories on the web server.
- Step 2: Move any sensitive office files to a secure location with restricted access.
- Step 3: Configure the web server to deny direct access to the original directory where the files were located. This can be done through .htaccess files or server configuration settings.
- Step 4: Verify that users requiring access to these files can still access them via a secure application or portal with appropriate authentication and authorisation.
4.3 Config or Code Example
Before
<Directory /var/www/html/documents>
Options Indexes FollowSymLinks
AllowOverride None
Require all granted
</Directory>After
<Directory /var/www/html/documents>
Options -Indexes FollowSymLinks
AllowOverride None
Require all denied
</Directory>4.4 Security Practices Relevant to This Vulnerability
Several security practices can help prevent this issue. Least privilege is essential for limiting the impact of a successful attack. Input validation can block attempts to access files directly. Secure defaults should be used when configuring web server access controls.
- Practice 1: Implement least privilege by granting only necessary permissions to users and applications accessing sensitive data.
- Practice 2: Use input validation on any forms or scripts that handle file paths to prevent attackers from manipulating URLs.
4.5 Automation (Optional)
#!/bin/bash
# This script finds office files in /var/www/html/documents and denies access via .htaccess
find /var/www/html/documents -type f ( -name "*.doc" -o -name "*.ppt" -o -name "*.xls" -o -name "*.pdf" ) -print0 | while IFS= read -r -d $' ' file; do
echo "Denying access to: $file"
echo "Require all denied" >> /var/www/html/.htaccess
done
# Caution: This script modifies .htaccess. Back up before running!5. Verification / Validation
Confirm the fix by checking that office files are no longer directly accessible via the web server. Re-run earlier detection methods to verify the issue is resolved.
- Post-fix check: Attempt to access a previously identified .doc file in your browser. You should receive a 403 Forbidden error.
- Re-test: Run the `ls` command from Section 3 and confirm no office files are listed in publicly accessible directories.
- Smoke test: Verify that any applications or portals requiring access to these files still function correctly with appropriate authentication.
- Monitoring: Check web server logs for failed requests attempting to access .doc, .ppt, .xls or .pdf files.
curl -I http://yourserver/documents/sensitive.doc6. Preventive Measures and Monitoring
Update security baselines to include restrictions on storing office documents in publicly accessible web server directories. Implement checks in your CI/CD pipeline to prevent the deployment of sensitive files. Establish a regular patch or configuration review cycle for web servers.
- Baselines: Update your CIS benchmark or GPO settings to deny direct access to common document file extensions on web servers.
- Pipelines: Add SAST tools to scan code repositories and prevent the commit of sensitive files.
- Asset and patch process: Review web server configurations weekly for any newly added office documents.
7. Risks, Side Effects, and Roll Back
- Risk or side effect 1: Applications relying on direct file access may stop working. Mitigation: Test thoroughly and provide alternative secure access methods.
- Roll back: Restore the backup of the web server file system, including the original .htaccess file.
8. References and Resources
- Vendor advisory or bulletin: Check your web server vendor’s security documentation for best practices on file access control.
- NVD or CVE entry: While there is no specific CVE, review CWE-590 for related information