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KB5004442—Manage changes for Windows DCOM Server Security Feature Bypass

KB5004442—Manage changes for Windows DCOM Server Security Feature Bypass

Registry setting to enable or disable the hardening changes

During the timeline phases in which you can enable or disable the hardening changes for CVE-2021-26414, you can use the following registry key:

  • Path : HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Ole\AppCompat
  • Value Name: “RequireIntegrityActivationAuthenticationLevel”
  • Type: dword
  • Value Data: default = 0x00000000 means disabled. 0x00000001 means enabled. If this value is not defined, it will default to enabled.

Note You must enter Value Data in hexadecimal format.

Important You must restart your device after setting this registry key for it to take effect.

 

Registry settings to raise the activation authentication level

You can use the following registry key to raise the activation authentication level.

  • Path : HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Ole\AppCompat
  • Value Name: “RaiseActivationAuthenticationLevel”
  • Type: dword
  • Value Data: 1 means raise default authentication level to RPC_C_AUTHN_LEVEL_PKT_INTEGRITY.

    Two (2) means raise authentication level for all non-anonymous activation requests to RPC_C_AUTHN_LEVEL_PKT_INTEGRITY if it is below Packet Integrity. This includes the explicitly set authentication level in activation functions, such as CoCreateInstanceEx. If this value is not defined, it will default to 1 (before November 8, 2022) and 2 (after November 8, 2022).

Note You must enter Value Data in hexadecimal format.

Important You must restart your device after setting this registry key for it to take effect.

Note This registry value does not exist by default; you must create it. Windows will read it if it exists and will not overwrite it.

New DCOM error events

To help you identify the applications that might have compatibility issues after we enable DCOM security hardening changes, we added new DCOM error events in the System log; see the tables below. The system will log these events if it detects that a DCOM client application is trying to activate a DCOM server using an authentication level that is less than RPC_C_AUTHN_LEVEL_PKT_INTEGRITY. You can trace to the client device from the server-side event log and use client-side event logs to find the application.

Server events

Event IDMessage
10036“The server-side authentication level policy does not allow the user %1\%2 SID (%3) from address %4 to activate DCOM server. Please raise the activation authentication level at least to RPC_C_AUTHN_LEVEL_PKT_INTEGRITY in client application.”

(%1 – domain, %2 – user name, %3 – User SID, %4 – Client IP Address)

Client events

Event IDMessage
10037“Application %1 with PID %2 is requesting to activate CLSID %3 on computer %4 with explicitly set authentication level at %5. The lowest activation authentication level required by DCOM is 5(RPC_C_AUTHN_LEVEL_PKT_INTEGRITY). To raise the activation authentication level, please contact the application vendor.”
10038“Application %1 with PID %2 is requesting to activate CLSID %3 on computer %4 with default activation authentication level at %5. The lowest activation authentication level required by DCOM is 5(RPC_C_AUTHN_LEVEL_PKT_INTEGRITY). To raise the activation authentication level, please contact the application vendor.”

(%1 – Application Path, %2 – Application PID, %3 – CLSID of the COM class the application is requesting to activate, %4 – Computer Name, %5 – Value of Authentication Level)

Availability

These error events are only available for a subset of Windows versions; see the table below.

 

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