1. Introduction
The SMTP settings vulnerability concerns the parameters used by other SMTP checks within a security testing system. These settings require a third-party host/domain for operation, and using default values like ‘example.edu’ can potentially leak packet traces from your network, compromising test privacy. This affects systems running security scanning tools that utilise SMTP checks, with potential impact on confidentiality through unintended data disclosure.
2. Technical Explanation
The vulnerability arises because several checks need to use a third-party host/domain name for proper function. The default configuration uses ‘example.edu’. While the owner of this domain is not known to log packet traces, using it creates a potential information leak. An attacker could passively monitor network traffic and identify systems testing against example.edu, revealing internal network details.
- Root cause: Use of a fixed default third-party SMTP host/domain name for checks.
- Exploit mechanism: A passive attacker monitors network traffic to identify hosts communicating with ‘example.edu’ during security tests.
- Scope: Systems running security scanning tools that rely on SMTP checks, regardless of operating system or specific product version.
3. Detection and Assessment
- Quick checks: Examine the scanner’s configuration interface or command-line options for SMTP settings. Look for ‘example.edu’ as the configured host.
- Scanning: Nessus plugin ID 16754 can identify this issue, but results should be verified manually.
- Logs and evidence: Check the scanning tool’s logs for connections to ‘example.edu’. The exact log file location varies by product.
# Example command placeholder:
# grep -r "example.edu" /path/to/scanner/config
4. Solution / Remediation Steps
Follow these steps to fix the issue.
4.1 Preparation
- Ensure you have access to modify the scanner’s configuration. A roll back plan is to restore the original configuration file.
- Change windows may be required depending on service impact. Approval from the IT security team might be necessary.
4.2 Implementation
- Step 1: Open the scanner’s configuration file or interface.
- Step 2: Locate the SMTP settings section.
- Step 3: Change the SMTP host/domain name from ‘example.edu’ to a third-party domain you control, or one that is unrelated to your network.
- Step 4: Save the changes and restart the scanner if required.
4.3 Config or Code Example
Before
smtp_host = example.edu
smtp_port = 25
After
smtp_host = yourdomain.com
smtp_port = 25
4.4 Security Practices Relevant to This Vulnerability
List only practices that directly address this vulnerability type. Use neutral wording and examples instead of fixed advice.
- Practice 1: Safe defaults – avoid using pre-configured values that could expose internal network information.
- Practice 2: Least privilege – limit the scanner’s access to only necessary resources, reducing potential impact if compromised.
4.5 Automation (Optional)
If suitable, provide a small script or infrastructure code that applies the fix at scale. Only include if safe and directly relevant.
# Example PowerShell snippet:
# Get-Content -Path "C:Scannerconfig.ini" | ForEach-Object { $_ -replace "smtp_host = example.edu", "smtp_host = yourdomain.com" } | Set-Content -Path "C:Scannerconfig.ini"
5. Verification / Validation
Confirm the fix worked by checking the scanner’s configuration and re-running tests.
- Post-fix check: Examine the scanner’s configuration interface or config file; ‘smtp_host’ should now be set to your chosen domain.
- Re-test: Run a scan and verify that connections are made to your new SMTP host, not example.edu.
- Monitoring: Check scanner logs for successful connections to the new SMTP host.
# Post-fix command and expected output:
# grep -r "smtp_host" /path/to/scanner/config
# smtp_host = yourdomain.com
6. Preventive Measures and Monitoring
Suggest only measures that are relevant to the vulnerability type.
- Baselines: Update security baselines or policies to require a custom SMTP host for scanning tools.
- Pipelines: Include configuration checks in CI/CD pipelines to prevent deployment of scanners with default settings.
- Asset and patch process: Regularly review scanner configurations as part of your asset management process.
7. Risks, Side Effects, and Roll Back
List known risks or service impacts from the change. Give short roll back steps.
- Risk or side effect 2: Using an unavailable SMTP host will cause scan failures. Verify the new host is reachable and functioning.
- Roll back: Restore the original scanner configuration file. Restart the scanner if required.
8. References and Resources
Link only to sources that match this exact vulnerability.
- Vendor advisory or bulletin: No specific vendor advisory available for this general issue.
- NVD or CVE entry: This is not a standard CVE, so no NVD entry exists.
- Product or platform documentation relevant to the fix: Refer to your scanner’s documentation for configuration details.