Schannel 36871 windows 11

I’ve often seen Windows Server administrators puzzled by recurring Schannel errors that disrupt daily operations. Let’s explore these error messages and clarify how to successfully troubleshoot them.

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Understanding Schannel Errors on Windows Server

Schannel errors, specifically Event ID 36871 and 36874, appear when there are problems with Windows’ TLS/SSL handshake processes. Schannel (Secure Channel) is a Windows security package responsible for secure communications using protocols like TLS 1.2. When a mismatch or misconfiguration arises, the server struggles to establish a secure channel, triggering error messages that can fill your Event Viewer logs.

Breaking Down the Error Messages

Event ID 36871

This error generally reads:

“A fatal error occurred while creating a TLS client credential. The internal error state is 10013 (or 10010).”

When you see these internal error codes, it usually indicates:

1. A mismatch between the server’s and client’s configured TLS versions.
2. An issue with the server’s cipher suites.
3. A certificate-related error, such as missing or invalid certificates.

Event ID 36874

The text often looks like:

“A TLS 1.2 connection request was received from a remote client application, but none of the cipher suites supported by the client application are supported by the server. The TLS connection request has failed.”

In this case, the client and server cannot agree on a mutual cipher suite, leading to a dropped connection. While Event ID 36874 is specifically about TLS 1.2, the core issue remains cipher suite mismatch or a lack of alignment in cryptographic settings.

Why These Errors Occur

There are several causes for Schannel issues on Windows Server:

1. Cipher Suite Conflicts

• If the server only allows newer, more secure cipher suites and the client attempts older or disabled suites, the handshake will fail. Conversely, if the server lacks robust cipher suites and the client requires something more modern, the same issue arises.

1. Disabled TLS Versions

• If the server registry settings disable TLS 1.2 or only partially enable it, Schannel can’t form a stable TLS 1.2 connection.

1. Misconfigured .NET Settings

• Certain applications that rely on the .NET Framework may require registry-based changes to enable strong cryptography, especially for TLS 1.2.

1. Certificate Problems

• Expired or invalid certificates, missing certificate chain intermediates, or using a certificate that doesn’t match the server’s fully qualified domain name (FQDN) can lead to these Schannel events.

1. Inconsistent Patch Levels

• Missing Windows updates or partial installation of security patches can cause cryptographic components to misbehave.

Symptoms and Potential Impact

Schannel errors don’t just clutter your Event Viewer logs; they can also cause:

• Application Downtime: Web applications or services that require TLS-secured communication might fail to connect.
• Remote Desktop Issues: If RDP relies on TLS for encryption, Schannel errors could potentially disrupt remote sessions.
• Email Services & Authentication Failures: Exchange or third-party mail servers that need encrypted channels could fail to send or receive messages properly.
• Performance Degradation: Repeated handshake attempts that fail can consume resources, leading to overall reduced server performance.

Common Observations

Many administrators have reported that enabling TLS 1.2 via registry and applying the latest Windows patches does not immediately clear these errors. In some instances, older protocols like SSL 3.0 or TLS 1.0 had been disabled, but certain clients or applications still depended on them. This mismatch can keep the errors occurring even with the best intentions to use only modern protocols.

Step-by-Step Solutions

Below are detailed methods to align your Windows Server settings, .NET configurations, and certificates to eliminate Schannel errors.

1. Verify and Align Cipher Suites

Start by confirming what cipher suites your Windows Server offers and ensuring they match at least one of the client-supported suites.

Using IIS Crypto or PowerShell

• IIS Crypto: A straightforward GUI tool from Nartac Software that lists protocols, ciphers, and hashes.
• PowerShell: On Windows Server 2019 and later, you can inspect cipher suite configuration using PowerShell cmdlets. For example:

  Get-TlsCipherSuite | Format-Table Name, Enabled, Priority
  

This reveals which cipher suites are enabled and their priority order.

Recommended Cipher Suites

Modern cipher suites typically include AES-based encryption with GCM mode. Examples:

• TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
• TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256

Ensure that older cipher suites using RC4, 3DES, or MD5 hashing are disabled to maintain stronger security. You can reorder them or remove insecure suites using IIS Crypto or through registry edits.

2. Configure Strong Cryptography in .NET

Many enterprise applications built on the .NET Framework rely on .NET’s cryptographic settings rather than just the OS-level Schannel configuration. To ensure .NET apps can use TLS 1.2, set the following registry keys:

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\.NETFramework\v2.0.50727]
"SystemDefaultTlsVersions" = dword:00000001
"SchUseStrongCrypto" = dword:00000001

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\.NETFramework\v4.0.30319]
"SystemDefaultTlsVersions" = dword:00000001
"SchUseStrongCrypto" = dword:00000001

Double-Check .NET Version Compatibility

• Applications running on older .NET Framework versions (e.g., 3.5) might not inherently support TLS 1.2.
• Confirm that your .NET environment supports TLS 1.2 or plan an upgrade if needed.

3. Enable TLS 1.2 in the Registry

Even though you might have TLS 1.2 enabled, it’s worth validating these registry paths:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Server
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Client

Make sure the following values are in place:

Why This Matters

Some hotfixes or group policy changes might reset these keys, causing the server or client side to revert to less secure defaults. If these keys are missing, create them with the appropriate values. Always back up your registry before modifications.

4. Check Certificates in the Server Certificate Store

Open the Certificate Manager (certlm.msc) on your Windows Server and review the Personal > Certificates section:

• Valid Dates: Ensure the certificate is current (not expired) and not close to expiration.
• Key Usage & Chain: Make sure the key usage includes server authentication, and the certificate chain is fully trusted.
• SAN (Subject Alternative Name): Confirm the FQDN or hostname matches the certificate’s SAN.

If your server is using multiple SSL certificates (e.g., for different subdomains), verify each one individually.

5. Keep Windows Updated

While you may have applied the latest monthly rollups, occasionally Microsoft releases targeted Schannel or TLS updates as part of cumulative or optional updates. Double-check Windows Update or WSUS to see if any optional security fixes address TLS handshake issues.

6. Confirm No Dependencies on Older Protocols

Modern security standards recommend disabling TLS 1.0, TLS 1.1, SSL 2.0, and SSL 3.0. However, if older applications or devices still rely on these protocols, the server might continue to log Schannel errors when they try to connect. A typical scenario is a legacy printer or scanner that only supports TLS 1.0, which fails to communicate properly with an updated Windows Server.

Advanced Troubleshooting Techniques

If none of the standard fixes solve your Schannel errors, you can delve deeper with the following:

1. Enable Schannel Event Logging

Schannel offers a debug logging feature to expose detailed handshake progress. You can enable it via registry:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\EventLogging

Set the EventLogging DWORD to 7. This will produce verbose logs in the System event log, helping you identify exactly which ciphers or protocols are attempted.

2. Use Network Monitoring Tools

• Wireshark: Capture traffic on the server to see the TLS handshake process in detail. This helps confirm which cipher suites are proposed by the client and accepted (or rejected) by the server.
• Microsoft Message Analyzer (Legacy): Although no longer actively developed, older environments might still rely on it to review Schannel connections.

3. Group Policy Overrides

In some domains, group policies might override local server registry settings. Check for any GPOs that specifically set cipher suites or TLS protocols:

1. Open the Group Policy Management Console (GPMC).
2. Review computer-based policies under “Administrative Templates” or “Security Settings.”
3. Look for settings related to “SSL Configuration Settings” or “Schannel” within the policy tree.

Even if you set registry keys locally, these can be overridden at the next GPO refresh interval.

Practical Example: Aligning Cipher Suites Step by Step

Below is an example table showing how an administrator might align cipher suites between a Windows Server 2022 and a legacy application server that also supports TLS 1.2:

When to Seek Additional Help

Some scenarios require deeper expertise:

• Custom or Legacy Applications: If you have custom-coded software that references legacy .NET frameworks or uses certain cryptography APIs, you may need developer intervention to recompile or update those applications.
• Strict Compliance Environments: If you’re managing environments subject to strict compliance standards (PCI-DSS, HIPAA, etc.), you must ensure that only authorized cipher suites and protocols are used while maintaining functionality.
• Repeated Certificate Failures: When certificates repeatedly fail or you see chain-of-trust issues, consider involving your Certificate Authority (CA) or a network security professional to re-provision your PKI (Public Key Infrastructure).

Frequently Asked Questions

Q1: Do I need to enable TLS 1.1 if TLS 1.2 is enabled?

A1: Generally, no. TLS 1.2 is more secure and is widely supported. You can safely disable older protocols like TLS 1.1 to maintain a strong security posture unless you have applications that strictly require them.

Q2: Why do these errors persist after applying Windows updates?

A2: Sometimes, post-update reboots or finalizing certain KB patches is necessary. Furthermore, registry changes might not be recognized until a reboot. Always verify that you’ve completed all steps and confirm the correct registry settings remain in place after an update.

Q3: Are there performance implications to using only newer cipher suites?

A3: In modern server hardware with optimized AES instructions, the performance impact of using advanced suites like AES-GCM is often negligible. In fact, they can be more efficient than older ciphers. Unless you’re dealing with extremely high-volume encryption or older hardware, performance is usually improved with modern suites.

Conclusion

Resolving Schannel Event IDs 36871 and 36874 on Windows Server 2022 or 2019 involves ensuring alignment in TLS versions, cipher suites, and certificate configurations. Begin with verifying your server’s TLS registry settings, matching cipher suites between client and server, and confirming that .NET applications are configured for strong cryptography. Keep your server patched, regularly review your certificate stores, and remain alert for older protocols still in use by legacy systems. By following these steps, you can maintain a secure, modern, and fully functional environment free from repetitive Schannel warnings.

If you continue seeing persistent issues even after implementing these measures, it may be time to delve deeper into advanced diagnostics with Wireshark or Schannel debug logs. In particularly challenging cases, Microsoft Support or a dedicated security consultant can help pinpoint the missing link in your TLS configuration.