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Considerations and known issues when using Credential Guard

Microsoft recommends that in addition to deploying Credential Guard, organizations move away from passwords to other authentication methods, such as Windows Hello for Business, FIDO 2 security keys, or smart cards.

Upgrade considerations

Important

Windows Server 2025 is in preview. This information relates to a prerelease product that may be substantially modified before it's released. Microsoft makes no warranties, expressed or implied, with respect to the information provided here.

As Credential Guard evolves and enhances its security features, newer versions of Windows running Credential Guard might affect previously functional scenarios. For instance, Credential Guard could restrict the use of certain credentials or components to thwart malware exploiting vulnerabilities.

It's advisable to thoroughly test operational scenarios within an organization before updating devices that utilize Credential Guard.

Upgrades to Windows 11, version 22H2, and Windows Server 2025 (preview) have Credential Guard enabled by default unless explicitly disabled.

Wi-fi and VPN considerations

When Credential Guard is enabled, you can no longer use NTLM classic authentication (NTLMv1) for single-sign-on (SSO). You'll be forced to enter your credentials to use these protocols and can't save the credentials for future use.

If you're using WiFi and VPN endpoints that are based on MS-CHAPv2, they're subject to similar attacks as for NTLMv1.

For WiFi and VPN connections, it's recommended to move from MSCHAPv2-based connections (such as PEAP-MSCHAPv2 and EAP-MSCHAPv2), to certificate-based authentication (such as PEAP-TLS or EAP-TLS).

Delegation considerations

When Credential Guard is enabled, certain types of identity delegation are unusable, as their underlying authentication schemes are incompatible with Credential Guard or require supplied credentials.

When Credential Guard is enabled, Credential Security Support Provider ("CredSSP") is no longer able to use saved or SSO credentials, though cleartext credentials can still be supplied. CredSSP-based Delegation requires cleartext credentials to be supplied on the destination machine, and doesn't work with SSO once Credential Guard is enabled and blocks cleartext credential disclosure. Usage of CredSSP for delegation, and in general, isn't recommended due to the risk of credential theft.

Kerberos Unconstrained delegation and DES are blocked by Credential Guard. Unconstrained delegation isn't a recommended practice.

Instead Kerberos or Negotiate SSP are recommended for authentication generally, and for delegation, Kerberos Constrained Delegation and Resource-Based Kerberos Constrained Delegation are recommended. These methods provide greater credential security overall, and are also compatible with Credential Guard.

Non-Microsoft Security Support Providers considerations

Some non-Microsoft Security Support Providers (SSPs and APs) might not be compatible with Credential Guard because it doesn't allow non-Microsoft SSPs to ask for password hashes from LSA. However, SSPs and APs still get notified of the password when a user logs on and/or changes their password. Any use of undocumented APIs within custom SSPs and APs aren't supported.

It's recommended that custom implementations of SSPs/APs are tested with Credential Guard. SSPs and APs that depend on any undocumented or unsupported behaviors fail. For example, using the KerbQuerySupplementalCredentialsMessage API isn't supported. Replacing the NTLM or Kerberos SSPs with custom SSPs and APs.

For more information, see Restrictions around Registering and Installing a Security Package.

Saved Windows credentials considerations

Credential Manager allows you to store three types of credentials:

  • Windows credentials
  • Certificate-based credentials
  • Generic credentials

Domain credentials that are stored in Credential Manager are protected with Credential Guard.

Generic credentials, such as user names and passwords that you use to sign in websites, aren't protected since the applications require your clear-text password. If the application doesn't need a copy of the password, they can save domain credentials as Windows credentials that are protected. Windows credentials are used to connect to other computers on a network.

The following considerations apply to the Credential Guard protections for Credential Manager:

  • Windows credentials saved by the Remote Desktop client can't be sent to a remote host. Attempts to use saved Windows credentials fail, displaying the error message Logon attempt failed
  • Applications that extract Windows credentials fail
  • When credentials are backed up from a PC that has Credential Guard enabled, the Windows credentials can't be restored. If you need to back up your credentials, you must do so before you enable Credential Guard

TPM clearing considerations

Virtualization-based Security (VBS) uses the TPM to protect its key. When the TPM is cleared, the TPM protected key used to encrypt VBS secrets is lost.

Warning

Clearing the TPM results in loss of protected data for all features that use VBS to protect data.

When a TPM is cleared, all features that use VBS to protect data can no longer decrypt their protected data.

As a result, Credential Guard can no longer decrypt protected data. VBS creates a new TPM protected key for Credential Guard. Credential Guard uses the new key to protect new data. However, the previously protected data is lost forever.

Note

Credential Guard obtains the key during initialization. The data loss will only impact persistent data and occur after the next system startup.

Windows credentials saved to Credential Manager

Since Credential Manager can't decrypt saved Windows Credentials, they're deleted. Applications should prompt for credentials that were previously saved. If saved again, then Windows credentials are protected Credential Guard.

Domain-joined device's automatically provisioned public key

Active Directory domain-joined devices automatically provision a bound public key, for more information about automatic public key provisioning, see Domain-joined Device Public Key Authentication.

Since Credential Guard can't decrypt the protected private key, Windows uses the domain-joined computer's password for authentication to the domain. Unless other policies are deployed, there shouldn't be a loss of functionality. If a device is configured to only use public key, then it can't authenticate with password until that policy is disabled. For more information on Configuring devices to only use public key, see Domain-joined Device Public Key Authentication.

Also if any access control checks including authentication policies require devices to have either the KEY TRUST IDENTITY (S-1-18-4) or FRESH PUBLIC KEY IDENTITY (S-1-18-3) well-known SIDs, then those access checks fail. For more information about authentication policies, see Authentication Policies and Authentication Policy Silos. For more information about well-known SIDs, see [MS-DTYP] Section 2.4.2.4 Well-known SID Structures.

Breaking DPAPI on domain-joined devices

On domain-joined devices, DPAPI can recover user keys using a domain controller from the user's domain. If a domain-joined device has no connectivity to a domain controller, then recovery isn't possible.

Important

Best practice when clearing a TPM on a domain-joined device is to be on a network with connectivity to domain controllers. This ensures DPAPI functions and the user does not experience strange behavior.

Auto VPN configuration is protected with user DPAPI. User might not be able to use VPN to connect to domain controllers since the VPN configurations are lost. If you must clear the TPM on a domain-joined device without connectivity to domain controllers, then you should consider the following.

Domain user sign-in on a domain-joined device after clearing a TPM for as long as there's no connectivity to a domain controller:

Credential Type Behavior
Certificate (smart card or Windows Hello for Business) All data protected with user DPAPI is unusable and user DPAPI doesn't work at all.
Password If the user signed in with a certificate or password prior to clearing the TPM, then they can sign-in with password and user DPAPI is unaffected.

Once the device has connectivity to the domain controllers, DPAPI recovers the user's key and data protected prior to clearing the TPM can be decrypted.

Impact of DPAPI failures on Windows Information Protection

When data protected with user DPAPI is unusable, then the user loses access to all work data protected by Windows Information Protection. The impact includes: Outlook is unable to start and work protected documents can't be opened. If DPAPI is working, then newly created work data is protected and can be accessed.

Workaround: Users can resolve the problem by connecting their device to the domain and rebooting or using their Encrypting File System Data Recovery Agent certificate. For more information about Encrypting File System Data Recovery Agent certificate, see Create and verify an Encrypting File System (EFS) Data Recovery Agent (DRA) certificate.

Known issues

Credential Guard blocks certain authentication capabilities. Applications that require such capabilities won't function when Credential Guard is enabled.

This article describes known issues when Credential Guard is enabled.

Live migration with Hyper-V breaks when upgrading to Windows Server 2025 (preview)

Important

Windows Server 2025 is in previeww. This information relates to a prerelease product that may be substantially modified before it's released. Microsoft makes no warranties, expressed or implied, with respect to the information provided here.

Devices that use CredSSP-based Delegation might no longer be able to use Live Migration with Hyper-V after upgrading to Windows Server 2025 (preview). Applications and services that rely on live migration (such as SCVMM) might also be affected. CredSSP-based delegation is the default for Windows Server 2022 and earlier for live migration.

Description
Affected devices Any server with Credential Guard enabled might encounter this issue. Starting in Windows Server 2025 (preview), Credential Guard is enabled by default on all domain-joined servers that aren't domain controllers. Default enablement of Credential Guard can be preemptively blocked before upgrade.
Cause of the issue Live Migration with Hyper-V, and applications and services that rely on it, are affected by the issue if one or both ends of a given connection try to use CredSSP with Credential Guard enabled. With Credential Guard enabled, CredSSP can only utilize supplied credentials, not saved or SSO credentials.

If the source machine of a Live Migration uses CredSSP for delegation with Credential Guard enabled, the Live Migration fails. In most cases, Credential Guard's enablement state on the destination machine won't impact Live Migration. Live Migration also fails in cluster scenarios (for example, SCVMM), since any device might act as a source machine.
Resolution Instead of CredSSP Delegation, Kerberos Constrained Delegation and Resource-Based Kerberos Constrained Delegation are recommended. These forms of delegation provide greater credential protections, in addition to being compatible with Credential Guard. Administrators of Hyper-V can configure these types of delegation manually or with the help of automated scripts.

Single sign-on for Network services breaks after upgrading to Windows 11, version 22H2 or Windows Server 2025 (preview)

Devices that use 802.1x wireless or wired network, RDP, or VPN connections that rely on insecure protocols with password-based authentication are unable to use SSO to sign in and are forced to manually reauthenticate in every new Windows session when Credential Guard is running.

Description
Affected devices Any device with Credential Guard enabled might encounter the issue. Starting in Windows 11, version 22H2, and Windows Server 2025 (preview), eligible devices that didn't disable Credential Guard, have it enabled by default. This affects all devices on Enterprise (E3 and E5) and Education licenses, and some Pro licenses, as long as they meet the minimum hardware requirements.

All Windows Pro devices that previously ran Credential Guard on an eligible license and later downgraded to Pro, and which still meet the minimum hardware requirements, receive default enablement.
Cause of the issue Applications and services are affected by the issue when they rely on insecure protocols that use password-based authentication. Such protocols are considered insecure because they can lead to password disclosure on the client or the server, and Credential Guard blocks them. Affected protocols include:

- Kerberos unconstrained delegation (both SSO and supplied credentials are blocked)
- Kerberos when PKINIT uses RSA encryption instead of Diffie-Hellman (both SSO and supplied credentials are blocked)
- MS-CHAP (only SSO is blocked)
- WDigest (only SSO is blocked)
- NTLM v1 (only SSO is blocked)

Note: Since only SSO is blocked for MS-CHAP, WDigest, and NTLM v1, these protocols can still be used by prompting the user to supply credentials.
Resolution Microsoft recommends moving away from MSCHAPv2-based connections (for example, PEAP-MSCHAPv2 and EAP-MSCHAPv2), to certificate-based authentication (for example, PEAP-TLS or EAP-TLS). Credential Guard doesn't block certificate-based authentication.

For a more immediate, but less secure fix, disable Credential Guard. Credential Guard doesn't have per-protocol or per-application policies, and it can either be turned on or off. If you disable Credential Guard, you leave stored domain credentials vulnerable to theft.

Tip

To prevent default enablement, configure your devices to disable Credential Guard before updating to a version which received default enablement. If the setting is not configured (which is the default state) and if the device is eligible, the device automatically enable Credential Guard after the update.

If Credential Guard is explicitly disabled, the device won't automatically enable Credential Guard after the update.

Note

To determine if a Windows Pro device receives default enablement when upgraded to Windows 11, version 22H2 or Windows Server 2025 (preview), check if the registry key IsolatedCredentialsRootSecret is present in Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0. If it's present, the device enables Credential Guard after the update.

Credential Guard can be disabled after upgrade by following the disablement instructions.

How to confirm the issue

MS-CHAP and NTLMv1 are relevant to the SSO breakage after the Windows 11, version 22H2 update. To confirm if Credential Guard is blocking MS-CHAP or NTLMv1, open the Event Viewer (eventvwr.exe) and go to Application and Services Logs\Microsoft\Windows\NTLM\Operational. Check the following logs:

Event ID (type)

Description

4013 (Warning)

<string
id="NTLMv1BlockedByCredGuard"
value="Attempt to use NTLMv1 failed.
Target server: %1%nSupplied user: %2%nSupplied domain: %3%nPID
of client process: %4%nName
of client process: %5%nLUID
of client process: %6%nUser identity
of client process: %7%nDomain name
of user identity of client process: %8%nMechanism OID: 9%n%n
This device doesn't support NTLMv1.
/>

4014 (Error)

<string
id="NTLMGetCredentialKeyBlockedByCredGuard"
value="Attempt to get credential key by call package blocked by Credential Guard.%n%n
Calling Process Name: %1%nService Host Tag: %2"
/>

Issues with non-Microsoft applications

The following issue affects MSCHAPv2:

The following issue affects the Java GSS API. See the following Oracle bug database article:

When Credential Guard is enabled on Windows, the Java GSS API doesn't authenticate. Credential Guard blocks specific application authentication capabilities and doesn't provide the TGT session key to applications, regardless of registry key settings. For more information, see Application requirements.

Vendor support

The following products and services don't support Credential Guard:

Important

This list isn't comprehensive. Check whether your product vendor, product version, or computer system supports Credential Guard on systems that run a specific version of Windows. Specific computer system models may be incompatible with Credential Guard.