1. Introduction
The Windows 10 / Windows Server 2016 September 2017 Information Disclosure vulnerability affects systems running these operating systems. It is a flaw where Microsoft scripting engines do not correctly handle objects in memory, potentially allowing an attacker to detect files on the user’s computer. This could lead to information disclosure, impacting confidentiality.
2. Technical Explanation
The vulnerability occurs because of missing security updates or incorrect registry settings for CVE-2017-8529. An attacker can host a malicious website that attempts to exploit this flaw when visited by an affected user. The scripting engine incorrectly processes objects, revealing file information. Preconditions include the user accessing a specially crafted web page with an affected browser.
- Root cause: Improper handling of objects in memory within Microsoft scripting engines.
- Exploit mechanism: An attacker hosts a website containing malicious script that attempts to detect files on the victim’s computer. The script exploits the vulnerability when executed by the user’s browser. For example, an attacker could use JavaScript to attempt to list directory contents.
- Scope: Windows 10 and Windows Server 2016 operating systems released in September 2017 are affected.
3. Detection and Assessment
You can confirm if a system is vulnerable by checking the installed updates or registry settings. A quick check involves verifying the OS build number, while a thorough method requires examining specific registry keys.
- Quick checks: Use `winver` to display the Windows version and build number.
- Scanning: Nessus ID 1f6a3c24 can detect this vulnerability as an example.
- Logs and evidence: Check system event logs for events related to scripting engine errors or unusual file access attempts, though specific event IDs are not consistently reported.
winver4. Solution / Remediation Steps
4.1 Preparation
- The roll back plan involves restoring the system from the created restore point or snapshot.
- A change window may be required depending on your organisation’s policies and impact assessment. Approval should be obtained from IT management.
4.2 Implementation
- Step 1: Install security update MS17-4038781.
- Step 2: Install security update MS17-4038782.
- Step 3: Install security update MS17-4038783.
- Step 4: Install security update MS17-4038788.
4.3 Config or Code Example
Before
(No specific configuration change is required, this vulnerability is addressed by installing security updates.)After
(Verify installed updates via Control Panel > Programs > Programs and Features > View Installed Updates)4.4 Security Practices Relevant to This Vulnerability
Practices like a regular patch cadence are important for preventing this issue. Least privilege can limit the impact if exploited.
- Practice 1: Implement a consistent patch management process to ensure timely application of security updates, reducing the window of exposure.
- Practice 2: Enforce least privilege principles, limiting user access rights to only what is necessary for their tasks. This reduces the potential damage if an attacker gains access.
4.5 Automation (Optional)
# Example PowerShell script to check for installed updates
Get-HotFix | Where-Object {$_.HotfixID -match "KB4038781" -or $HotfixID -match "KB4038782" -or $HotfixID -match "KB4038783" -or $HotfixID -match "KB4038788"}
# Note: This script only checks for installed updates, it does not install them.5. Verification / Validation
Confirm the fix by verifying that the relevant security updates are installed and re-running a vulnerability scan. Perform basic service tests to ensure functionality remains intact.
- Post-fix check: Run `Get-HotFix` in PowerShell and confirm KB4038781, KB4038782, KB4038783, and KB4038788 are listed.
- Re-test: Re-run the Nessus scan (ID 1f6a3c24) to confirm it no longer reports the vulnerability.
- Monitoring: Monitor system event logs for any unusual scripting engine activity or errors, though specific alerts are not defined.
Get-HotFix | Where-Object {$_.HotfixID -match "KB4038781" -or $HotfixID -match "KB4038782" -or $HotfixID -match "KB4038783" -or $HotfixID -match "KB4038788"}6. Preventive Measures and Monitoring
Update your security baselines to include the required updates. Implement automated patch management pipelines to prevent similar issues in the future.
- Baselines: Update your Windows baseline configuration to require these specific updates, ensuring all systems meet a minimum security standard.
- Asset and patch process: Review and update your asset inventory and patch management schedule to ensure timely application of critical security updates. A monthly review cycle is recommended.
7. Risks, Side Effects, and Roll Back
Applying updates carries a small risk of service disruption. Ensure you have a roll back plan in place.
- Risk or side effect 1: Updates may require system restarts, causing temporary downtime.
8. References and Resources
- Vendor advisory or bulletin: https://support.microsoft.com/kb/4038781
- NVD or CVE entry: /cve/CVE-2017-8529
- Product or platform documentation relevant to the fix: https://support.microsoft.com/en-