After installing .NET security patches to address CVE-2018-8421, SharePoint crawler may fail
APPLIES TO: 
2013 2016 2019 Subscription Edition 
SharePoint in Microsoft 365
Symptoms:
After applying September 2018 .NET 4.6 or later updates, the crawl will fail and you'll see similar following entries:
<date> <time> mssdmn.exe (0x2730) 0x00D8 SharePoint Foundation Database fa45 High System.TypeInitializationException: The type initializer for 'System.Data.SqlClient.SqlConnection' threw an exception. ---> System.IO.FileNotFoundException: C:\Program Files\Microsoft Office Servers\16.0\bin\mssdmn.exe at System.Diagnostics.FileVersionInfo.GetVersionInfo(String fileName) at System.Configuration.ClientConfigPaths.SetNamesAndVersion(String applicationFilename, Assembly exeAssembly, Boolean isHttp) at
System.Configuration.ClientConfigPaths..ctor(String exePath, Boolean includeUserConfig) at System.Configuration.ClientConfigPaths.GetPaths(String exePath, Boolean includeUserConfig) at System.Configuration.ClientConfigurationHost.RequireCompleteInit(IInternalConfigRecord
record) at System.Configuration.BaseConfigurationRecord.GetSectionRecursive(String configKey, Boolean getLkg, Boolean checkPermission, Boolean getRuntimeObject, Boolean requestIsHere, Object& result, Object& resultRuntimeObject) at
System.Configuration.BaseConfigurationRecord.GetSection(String configKey) at System.Configuration.ConfigurationManager.GetSection(String sectionName) at System.Data.SqlClient.SqlConnection..cctor() --- End of inner exception stack trace --- at
System.Data.SqlClient.SqlConnection..ctor(String connectionString) at Microsoft.SharePoint.Utilities.SqlSession.OpenConnection() at Microsoft.SharePoint.Administration.SPConfigurationDatabase.get_Local() at Microsoft.SharePoint.Administration.SPFarm.FindLocal(SPFarm& farm,
Boolean& isJoined)
<date> <time> mssdmn.exe (0x2730) 0x12E0 SharePoint Foundation Topology 88bl Monitorable An exception occurred while trying to acquire the local farm: System.TypeInitializationException: The type initializer for 'System.Data.SqlClient.SqlConnection' threw an exception. ---> System.IO.FileNotFoundException: C:\Program Files\Microsoft Office Servers\16.0\bin\mssdmn.exe at System.Diagnostics.FileVersionInfo.GetVersionInfo(String fileName) at System.Configuration.ClientConfigPaths.SetNamesAndVersion(String applicationFilename, Assembly exeAssembly,
Boolean isHttp) at System.Configuration.ClientConfigPaths..ctor(String exePath, Boolean includeUserConfig) at System.Configuration.ClientConfigPaths.GetPaths(String exePath, Boolean includeUserConfig) at
System.Configuration.ClientConfigurationHost.RequireCompleteInit(IInternalConfigRecord record) at System.Configuration.BaseConfigurationRecord.GetSectionRecursive(String configKey, Boolean getLkg, Boolean checkPermission, Boolean getRuntimeObject, Boolean requestIsHere, Object& result,
Object& resultRuntimeObject) at System.Configuration.BaseConfigurationRecord.GetSection(String configKey) at System.Configuration.ConfigurationManager.GetSection(String sectionName) at System.Data.SqlClient.SqlConnection..cctor() --- End of inner exception stack trace ---
at System.Data.SqlClient.SqlConnection..ctor(String connectionString) at Microsoft.SharePoint.Utilities.SqlSession.OpenConnection() at Microsoft.SharePoint.Administration.SPConfigurationDatabase.get_Local() at
Microsoft.SharePoint.Utilities.SqlSession.ExecuteReader(SqlCommand command, CommandBehavior behavior, SqlQueryData monitoringData, Boolean retryForDeadLock) at Microsoft.SharePoint.Utilities.SqlSession.ExecuteReader(SqlCommand command, Boolean retryForDeadLock) at Microsoft.SharePoint.Utilities.SqlSession.ExecuteReader(SqlCommand command) at Microsoft.SharePoint.Upgrade.SPDatabaseSequence.GetVersion(SPDatabase database, Guid id, Version defaultVersion, SqlSession session, SPDatabaseSequence sequence) at Microsoft.SharePoint.Upgrade.SPDatabaseSequence.get_SchemaVersion() at Microsoft.SharePoint.Upgrade.SPSequence.get_IsBackwardsCompatible() at Microsoft.SharePoint.Upgrade.SPUpgradeSession.IsBackwardsCompatible(Object o, Boolean bRecurse)
Cause:
The configuration section for SqlColumnEncryptionEnclaveProviders isn't defined but it's required by .NET Sql Client.
Solution 1:
Create a config file for mssdmn.exe if it doesn't exist already (by default it doesn't). Ensure the config file has the following content:
Content of mssdmn.exe.config:
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<configSections>
<section name="SqlColumnEncryptionEnclaveProviders"
type="System.Data.SqlClient.SqlColumnEncryptionEnclaveProviderConfigurationSection, System.Data, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
</configSections>
</configuration>
Normally the file should be located here:
SharePoint 2013: C:\Program Files\Microsoft Office Servers\15.0\bin\mssdmn.exe.config
SP 2016 and SP 2019: C:\Program Files\Microsoft Office Servers\16.0\bin\mssdmn.exe.config
Solution 2:
Solution 1 may fix the problem for search, but it's possible that you still see the problems with other components. If you still see the problems with other components, you can modify machine.config to include the change.
The following script will make the changes automatically. You must run this on all servers that have the problem.
<#
Copyright (c) Microsoft Corporation. All rights reserved.
MIT License
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the ""Software""), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED *AS IS*, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
#>
function Add-SQLEntry([string]$path)
{
# Load machine.config file
Write-Host "*** Config file: $path ***"
$config = [xml](Get-Content $path -ErrorAction Stop)
# Confirm whether the entry is already there
$node = (Select-Xml -xml $config -xpath '//configuration/configSections/section[@name="SqlColumnEncryptionEnclaveProviders"]');
if($node -ne $null)
{
Write-Host "1. Entry was already present";
Write-Host "2. No change necessary"
return $false
}
Write-Host "1. Entry for SqlColumnEncryptionEnclaveProviders is missing";
$newNode = $config.CreateElement('section');
$newNode.SetAttribute('name','SqlColumnEncryptionEnclaveProviders');
$newNode.SetAttribute('type','System.Data.SqlClient.SqlColumnEncryptionEnclaveProviderConfigurationSection, System.Data, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089');
$node = $config.SelectSingleNode('//configuration/configSections');
$node.AppendChild($newNode);
Write-Host "2. Adding entry"
Write-Host "3. Backing up machine.config"
# Make a backup of machine.config
$addDate = (Get-Date).ToString('yyyyMMddHHmmssfff')
Rename-Item -Path $path -NewName "$path.$addDate" -ErrorAction Stop
Write-Host "4. Saving changes";
$config.Save($path);
Write-Host "5. Changes saved successfully"
Write-Host ""
& notepad $path
return $true
}
$confPath32 = "$($env:windir)\Microsoft.NET\Framework\v4.0.30319\config\machine.config";
$confPath64 = "$($env:windir)\Microsoft.NET\Framework64\v4.0.30319\config\machine.config";
$addDate = (Get-Date).ToString('yyyyMMddHHmmssfff')
$success = Add-SQLEntry $confPath64
$success = Add-SQLEntry $confPath32