Windows Error Reporting (WER) Elevation of Privilege Vulnerability (CVE-2019-0863) Technical Analysis and Mitigation Guide
Executive & SecOps Summary
SECOPS ASSESSMENTMultiple versions of Windows operating systems, including Windows 7, 8.1, 10, and Windows Server 2008, 2012, 2016, 2019
A local attacker with low privileges can exploit the file handling mechanism of Windows Error Reporting (WER) to execute arbitrary code with SYSTEM privileges, leading to full system compromise
Immediately apply the official Microsoft security patches, and monitor for unauthorized symbolic link creation or anomalous file writes in the WER directories
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Apply the latest cumulative security updates provided by Microsoft. Use the following PowerShell commands to verify patch status and force Windows Update if necessary.
# Check if the relevant security update (e.g., KB4494441 for Windows 10 1809) is installed
Get-HotFix | Where-Object { $_.HotFixID -match 'KB4494441|KB4495667|KB4497934' }
# Install and force Windows Update using the PSWindowsUpdate module
Install-Module PSWindowsUpdate -Force -SkipPublisherCheck
Get-WindowsUpdate -AcceptAll -Install -AutoReboot2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, mitigate the risk by disabling the Windows Error Reporting service and restricting access to the WER directories.
# Stop and disable the Windows Error Reporting Service
Stop-Service -Name 'WerSvc' -Force
Set-Service -Name 'WerSvc' -StartupType Disabled
# Disable Windows Error Reporting via Registry Policy
New-Item -Path 'HKLM:\SOFTWARE\Policies\Microsoft\Windows' -Name 'Windows Error Reporting' -Force
New-ItemProperty -Path 'HKLM:\SOFTWARE\Policies\Microsoft\Windows\Windows Error Reporting' -Name 'Disabled' -Value 1 -PropertyType DWord -Force3. Log Audit & IoC Verification Commands
Monitor the WER directory for suspicious symbolic links or unauthorized file modifications by running the following audit script.
# Inspect the WER Temp directory for anomalous files or links
$WerPath = 'C:\ProgramData\Microsoft\Windows\WER\Temp'
if (Test-Path $WerPath) {
Get-ChildItem -Path $WerPath -Recurse -ErrorAction SilentlyContinue |
Select-Object FullName, CreationTime, LastWriteTime |
Format-Table -AutoSize
}
# Query Security Event Logs for Event ID 4663 (Object Access) targeting WER paths
Get-WinEvent -FilterHashtable @{
LogName='Security';
Id=4663;
StartTime=(Get-Date).AddDays(-7)
} -ErrorAction SilentlyContinue |
Where-Object { $_.Message -like '*\Windows\WER\*' } |
Select-Object TimeCreated, Id, Message | Out-StringBlock Kernel Privilege Escalation & Ransomware Payloads Before You Can Reboot
Protect unpatched Windows, Linux, and macOS workloads against in-memory exploitation and lateral movement with autonomous EDR.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability is an elevation of privilege (EoP) flaw in the way the Windows Error Reporting (WER) service handles files and directories. Because the WER service runs under the highly privileged 'NT AUTHORITY\SYSTEM' context, it must securely handle files generated during crash reporting. However, a design flaw exists where the service fails to properly validate file paths and ownership when creating temporary files in user-writable directories, making it vulnerable to Time-of-Check to Time-of-Use (TOCTOU) race conditions and symbolic link redirection.
2. Exploitation Mechanics & Attack Scenario
An attacker with local access and low-integrity privileges initiates the exploit by deliberately triggering an application crash to invoke the WER mechanism. As the WER service attempts to write temporary crash reports to C:\ProgramData\Microsoft\Windows\WER\Temp, the attacker exploits a race condition to replace the target directory or file with a symbolic link pointing to a critical system file (such as a system DLL or service executable). Consequently, the privileged WER service modifies the DACL (Discretionary Access Control List) of the target file or overwrites it with the attacker's payload, allowing the attacker to execute arbitrary code as SYSTEM.
3. Infrastructure & Business Impact
As a vulnerability listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, CVE-2019-0863 has been actively exploited in the wild. It serves as a critical post-exploitation vector for threat actors who have already established an initial foothold on an endpoint and seek to escalate privileges to perform lateral movement, disable security controls, or deploy ransomware with administrative privileges.
Official Vendor Advisories & References
An elevation of privilege vulnerability exists in the way Windows Error Reporting (WER) handles files, aka 'Windows Error Reporting Elevation of Privilege Vulnerability'.
Frequently Asked SecOps Questions (CVE-2019-0863)
FAQQ1. How critical is CVE-2019-0863 and is it actively exploited in the wild?
CVE-2019-0863 is rated CVSS 7.8 (HIGH) with a 30-day EPSS exploitation probability of 5.2%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2019-0863?
Primary impacted vendors include microsoft across windows, windows_server. Scope summary: All supported and legacy Windows OS versions, including Windows 7, 8.1, 10, and Windows Server 2008, 2012, 2016, 2019
Q3. What temporary mitigations or workarounds exist for CVE-2019-0863 before patching?
[Mitigation] Immediately apply the official Microsoft security patches, and monitor for unauthorized symbolic link creation or anomalous file writes in the WER directories Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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