After June 8, 2022, DCOM connections to Hyper-V, Veeam Backup & Replication, and other Windows-based servers may be impacted by the DCOM hardening policy activated after the deployment of the Microsoft CVE-2021-26414 security update.

The possibly affected products are:

• Veeam Backup & Replication — operations involving Hyper-V infrastructure may fail with the error:
  

  Failed to call RPC function 'HviCreateVmRecoverySnapshot'
  

• Veeam Agent for Microsoft Windows — connection to Hyper-V infrastructure fails with error:
  

  Failed to connect to cluster 'CLUSTERNAME.contoso.com'.
  

• Veeam ONE — connection to Hyper-V and Veeam Backup & Replication infrastructures fails with the error:
  

  System.UnauthorizedAccessException:'Access denied. (Exception from HRESULT : 0x80070005 (E_ACCESSDENIED))'
  

To resolve these issues, ensure that all Windows-based servers have the DCOM Hardening update installed. See the list at the bottom of this article:

• KB5004442—Manage changes for Windows DCOM Server Security Feature Bypass (CVE-2021-26414) 
  

Note: These updates may be listed as optional and may have been ignored by Windows or WSUS systems. In such a situation, the update must be deployed manually.

Veeam acknowledges that there is a registry value noted on KB5004442 that allows the DCOM hardening policy to be temporarily disabled. While the registry value may resolve the DCOM authentication conflict causing errors in Veeam, we strongly advise against implementing this workaround. The Veeam software is ready for this DCOM change and uses Packet Integrity DCOM authentication, it is the underlying Windows OS that must be updated to support this change.