Tenant Cloud Compute Cloud Virtual Machine Troubleshooting Windows Instances: An Authentication Error Occurred

Windows Instances: An Authentication Error Occurred

Last Updated At: 2025-11-26 11:12:15

Problem Description

When you log in to a Windows instance through a remote desktop connection, the following error message may appear:

  • An authentication error occurred. Invalid flags were provided to the feature.
  • An authentication error occurred. The requested feature is not supported.

Issue Analysis

Microsoft released a security update in March 2018 to address a remote code execution vulnerability in CredSSP by correcting the protocol and the way requests are validated during authentication. Both the client and the server must install this update; otherwise, the issue can occur.

The following three scenarios cause remote connection failure:

  • Scenario 1: Client not patched, server updated, policy set to Force updated clients.
  • Scenario 2: Server not patched, client updated, policy set to Force updated clients.
  • Scenario 3: Server not patched, client updated, policy set to Mitigate.
Note:

If you only want to upgrade the client locally, please refer to Solution 1: Install security updates (recommended).

Logging in to the CVM via VNC

  1. Log in to the CVM console.
  2. On the instance management page, find the target CVM instance and click Log In.
  3. In the pop-up Log in to Windows Instance window, select Other methods (VNC) and click Log in now.
  4. In the login window that pops up, select Send Remote Command in the upper left corner and click Ctrl-Alt-Delete to enter the system log-in interface.

Solution 1: Install Security Updates (Recommended)

Install security updates to update unpatched clients or servers.

  • Windows Server 2012: Control Panel > System and Security > Windows Update
  • Windows Server 2008: Start > Control Panel > System and Security > Windows Update
  • Windows 10: > Settings > Update & Security
  • Windows 7: > Control Panel > System and Security > Windows Update

Steps:

  1. Click and select Settings.
  2. In the Settings window, select Update & Security.
  3. In Windows Update, click Check for updates.
  4. Follow the interface instructions and click Start Installation.
  5. After installation, restart the instance.

Solution 2: Modifying the Policy

On machines with the security update installed, set the Encryption Oracle Remediation policy to Vulnerable.

Note:

Windows 10 Home does not have Group Policy Editor; use Solution 3 to modify the registry.

Steps:

  1. Press Win+R, enter gpedit.msc, and press Enter to open the Local Group Policy Editor.
  2. Navigate:
    Computer Configuration > Administrative Templates > System > Credentials Delegation
  3. Double-click Encryption Oracle Remediation, select Enabled, and set Protection Level to Vulnerable.
  4. Click OK and restart the instance.

Solution 3: Modifying the Registry

  1. Press Win+R, enter regedit, and press Enter to open the Registry Editor.
  2. Navigate or create the path:
    Computer > HKEY_LOCAL_MACHINE > SOFTWARE > Microsoft > Windows > CurrentVersion > Policies > System > CredSSP > Parameters
  3. Right-click Parameters, select New > DWORD (32-bit) Value, and name it AllowEncryptionOracle.
  4. Double-click AllowEncryptionOracle, set Value data to 2, and click OK.
  5. Restart the instance.