Hyper-V Remote Access Fails After CredSSP Patch

Question

How can I restore remote Hyper-V Manager access without weakening the CredSSP security fix?

Answer 1

Hi @Jie Jun

The CredSSP security updates were introduced to mitigate the encryption oracle vulnerability (CVE-2018-0886). Microsoft recommends keeping the mitigation enabled and updating all clients and servers rather than weakening the policy.

To restore remote Hyper-V Manager access, verify the following:

• Ensure both the Hyper-V host and the client are fully patched. A mismatch between patched and unpatched systems is the most common cause of CredSSP authentication failures.
• Verify WinRM and Hyper-V remote management are configured correctly on the host: Enable-PSRemoting -Force Also ensure the required firewall rules are enabled.
• Use Kerberos authentication when both systems are joined to the same Active Directory domain. If they're in a workgroup, configure TrustedHosts or use HTTPS for WinRM instead of relaxing CredSSP policies.
• If using CredSSP delegation, confirm it's configured on both the client and server:
  • Enable-WSManCredSSP -Role Client -DelegateComputer <HyperVHost>
  • Enable-WSManCredSSP -Role Server
• Avoid changing the Encryption Oracle Remediation policy to Vulnerable, as this disables the protection provided by the CredSSP security update. The recommended setting is Mitigated (or the default policy) after all systems have been updated.

To help narrow down the issue, could you provide:

• Are the client and Hyper-V host domain-joined or in a workgroup?
• What is the exact error message displayed in Hyper-V Manager?
• Which versions of Windows Server and Windows are running on the host and client?

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