Challenge
A backup job fails with the error:
PKCS12 (PFX) without a supplied password has exceeded maximum allowed iterations. See https://go.microsoft.com/fwlink/?linkid=2233907 for more information
The issue may also manifest as a backup job being stuck in the queued state. In this specific case, the UI's session log might not have a clear error, but if the stuck job issue began occurring after June 2023, it is likely related to the Microsoft updates in question. To further validate that this KB is relevant to that stuck job state, check the proxy log for the error shown above. The proxy log can be found in 'C:\ProgramData\Veeam\Backup365\Logs' on the Backup Proxy associated with the job. The log file has the following name pattern: Veeam.Archiver.Proxy_yyyy_mm_dd_hh_mm_ss.log
Cause
This error is reported by Veeam Backup for Microsoft 365 from the underlying .NET Framework, and is a known issue of KB5027124 Cumulative Update for .NET Framework 3.5 and 4.8 for Windows 10, version 1809 and Windows Server 2019.
Solution
Follow the instructions provided by Microsoft on the page in the error message (https://go.microsoft.com/fwlink/?linkid=2233907) to apply one of the solutions.
No actions within Veeam Backup for Microsoft 365 are required.
