How to remediate – WMI QuickFixEngineering (QFE) Enumeration

1. Introduction

The WMI QuickFixEngineering (QFE) Enumeration vulnerability means Windows systems are reporting details of installed quick-fix engineering updates. This information could help an attacker understand a system’s patch level and identify potential weaknesses. Affected systems are typically standard Windows servers and workstations. A successful exploit may allow for targeted attacks based on known vulnerabilities in older patches, impacting confidentiality, integrity, and availability.

2. Technical Explanation

This issue occurs because the Windows Management Instrumentation (WMI) service allows enumeration of installed QFE updates with appropriate credentials. An attacker gaining access to a system can query WMI to identify which quick fixes are present. There is no known CVE associated with this specific enumeration, but it’s a reconnaissance step often preceding exploitation of unpatched vulnerabilities. For example, an attacker could use PowerShell to list the installed hotfixes and then search for publicly known flaws in those versions.

• Root cause: WMI exposes update information accessible via standard queries.
• Exploit mechanism: An attacker connects to a remote system with valid credentials and uses WMI to retrieve QFE details. A simple PowerShell command can list the installed updates.
• Scope: All Windows systems running with WMI enabled are potentially affected.

3. Detection and Assessment

You can check for this by listing installed hotfixes on a system. A thorough method involves reviewing event logs for suspicious WMI activity.

• Quick checks: Use PowerShell to list installed updates. Get-HotFix
• Scanning: Nessus plugin ID 16857 can identify systems reporting QFE information. This is an example only.
• Logs and evidence: Check the Windows Event Log for events related to WMI activity, specifically event IDs 403 and 405 in the Microsoft-Windows-WMI-Activity/Operational log.

Get-HotFix | Select-Object HotfixID, Description, InstalledOn

4. Solution / Remediation Steps

The primary remediation is to restrict access to WMI or monitor for unusual activity. There isn’t a direct patch for this enumeration issue itself.

4.1 Preparation

• Ensure you have valid credentials to access the system if needed for roll back. A roll back plan is to restore from the pre-change snapshot.
• Changes may require a standard change window and approval from IT security.

4.2 Implementation

1. Step 1: Review local user accounts with access to WMI. Limit permissions where possible using Group Policy or Local Security Policy.
2. Step 2: Implement auditing of WMI activity to detect unauthorized queries. Configure event logging for WMI events.
3. Step 3: Consider disabling remote WMI access if not required by legitimate applications.

4.3 Config or Code Example

Before

# No specific WMI access restrictions in place

After

# Group Policy setting: Computer ConfigurationWindows SettingsSecurity SettingsLocal PoliciesUser Rights AssignmentAccess this computer from the network. Remove unnecessary accounts.

4.4 Security Practices Relevant to This Vulnerability

Least privilege and monitoring are key practices here. Least privilege reduces the impact if an attacker gains access, while monitoring detects suspicious activity.

• Practice 1: Implement least privilege principles by granting users only the minimum necessary permissions.
• Practice 2: Regularly monitor system logs for unusual WMI activity or unauthorized access attempts.

4.5 Automation (Optional)

You can use PowerShell to script auditing of WMI events and report on changes in user rights assignments.

# Example PowerShell script to audit WMI event logs:
# Get-WinEvent -LogName Microsoft-Windows-WMI-Activity/Operational | Where-Object {$_.ID -eq 403 -or $_.ID -eq 405} | Format-Table TimeCreated, ID, Message

5. Verification / Validation

Confirm the fix by checking WMI access restrictions and verifying event logging is enabled. Re-run the initial check to ensure updates are no longer easily enumerated.

• Post-fix check: Run Get-HotFix as a standard user. Access should be limited or denied based on your configuration.
• Re-test: Verify that running Get-HotFix with elevated privileges still works for administrators, but is restricted for other accounts.
• Monitoring: Create a lightweight log query to alert on event IDs 403 and 405 in the Microsoft-Windows-WMI-Activity/Operational log, indicating potential unauthorized access attempts. This is an example only.

Get-HotFix

6. Preventive Measures and Monitoring

Update security baselines to include WMI access restrictions. Add checks in deployment pipelines to ensure secure configurations are maintained.

• Baselines: Update your Windows security baseline or CIS control settings to enforce least privilege for WMI access.
• Pipelines: Include configuration validation steps in CI/CD pipelines to detect deviations from the approved WMI configuration.
• Asset and patch process: Review system configurations regularly as part of a standard patch management cycle.

7. Risks, Side Effects, and Roll Back

Restricting WMI access could break applications relying on it. The roll back steps involve restoring the original permissions or re-enabling remote WMI access.

• Risk or side effect 2: Disabling remote WMI access could impact remote management tools.
• Roll back: Step 1: Restore the original user rights assignments using Group Policy or Local Security Policy. Step 2: Re-enable remote WMI access if previously disabled.

8. References and Resources

• Vendor advisory or bulletin: http://www.nessus.org/u?0c4ec249
• NVD or CVE entry: No specific CVE associated with this enumeration issue.
• Product or platform documentation relevant to the fix: https://learn.microsoft.com/en-gb/windows-server/administration/wmi/