Veeam B&R backup jobs failed to login to Qnap Nas after KB5011503 installed

Copper Contributor

Good Morning, 
Veeam backup & Replication CE 11 (last release) installed on Windows Server 2019 Hyper-V VM from about 1 month
Veeam Backup jobs use as destination a shared folder on Qnap Nas.
Windows 2019 VM Italian language standalone, Qnap Nas under domain.
R&W user used for Qnap autentication it's local user for Qnap and Administrator for Win2019 VM.
All go fine before KB5011503 update
After this installation Veeam Backup job works only with guest user.
No other user can autenticate to Qnap with SMB 1, 2, 3
Error message on Qnap is 
"Processing MACHINENAME Error: Nome utente o password non corretta --tr:Error code: 0x0000052e Failed to process [isFileExists]. --tr:Client failed to process the command. Command: [isFileExists]. --tr:event:3:"

Trying to uninstal KB5011503 update, after reboot all veeam Backup Job returns to work.
Updating KB5011503 again all Job stop to work.
Could be this a bug?
Where I can report this to microsoft?

7 Replies



I created a new user on the QNAP and assigned it to the Veeam repository, all fine now.



Same issue here. Did you find any solution except uninstalling the Cumulative Win 2019 Server patch from March 2022?


Creating a new Qnap user didn't worked for me.

I find the same problem when I integrate my Qnap Nas into a local domain controller, The solution I made is by creating an AD user and giving him permission for the NAS share folder.


I found a solution:


Qnap domain joined.

Veeam Community Edition in a server domain joined.

QNAP is the backup connected to veeam using a local user of the qnap in this format:

user = username

pass = password

I was having the same problem.

SOLUTION that immediately worked for me:


In the backup repository of veeam, in the credential set of the QNAP mapped repo of veeam I used this format:

user = QNAPHOSTNAME\username

pass = password


Problem solved.



Thank you! Definitely the solution.

My QNAP was in the domain, AD users are recognized but I still had an error.

I can add the backup repository with a local QNAP account with read/write rights on the backup folder without specifying the "QNAPHOSTNAME" or an AD user but I could not perform the backups.


By specifying "QNAPHOSTNAME" the problem had disappeared.