Checkbox Survey Remote Code Execution (RCE) Vulnerability Analysis and Mitigation Guide (CVE-2021-27852)

# Verify the current version of CheckboxWeb.dll in your installation directory
(Get-Item 'C:\inetpub\wwwroot\Checkbox\bin\CheckboxWeb.dll').VersionInfo.FileVersion

# Apply the official upgrade package to migrate to a secure version.
# (Note: Ensure thorough compatibility testing in a staging environment before production deployment.)

<!-- Add this rewrite rule inside the <system.webServer> section of your web.config file -->
<configuration>
  <system.webServer>
    <rewrite>
      <rules>
        <rule name='Block External Access to Checkbox Admin' stopProcessing='true'>
          <match url='^(admin|api/v1/admin)' />
          <conditions>
            <add input='{REMOTE_ADDR}' pattern='^192\.168\.' negate='true' />
          </conditions>
          <action type='CustomResponse' statusCode='403' statusReason='Forbidden' statusDescription='Access Denied' />
        </rule>
      </rules>
    </rewrite>
  </system.webServer>
</configuration>

# Search IIS logs for suspicious POST requests targeting potential deserialization endpoints
Select-String -Path 'C:\inetpub\logs\LogFiles\W3SVC1\*.log' -Pattern 'POST' | Select-Object -First 50

# Monitor and detect if w3wp.exe has spawned suspicious child processes like cmd.exe or powershell.exe
Get-CimInstance Win32_Process -Filter "Name = 'cmd.exe' or Name = 'powershell.exe'" | 
Where-Object { (Get-Process -Id $_.ParentProcessId).ProcessName -eq 'w3wp' } | 
Select-Object ProcessId, CommandLine, CreationDate