KB4835

[Bubblebop]

Craziest thing I have experienced, we figured this out randomly yesterday.

Colleague had moved 1 TB of data but then in the backup report saw only a few MB and a Success message...

0 notifications from veeam, i had to manually find kb4835.

I have notification for kb4869 yesterday and KB4821 in february.

Hope this fix is not Soon™, does the managers know?

I made a forum account just to post this

[Polina]

Hi Bubble Bop,

Could you please elaborate which data have you moved, how and where? Cause it's not entirely clear atm how it is related to the issue from KB4835.

We have sent email notifications on KB4835 to all customers quite a while ago. If you didn't receive it, we can check if the issue is on our side so that it never happened again.

Thanks!

[Bubblebop]

Hi,

My colleague transferred from the customer's on-prem SMB to SharePoint.

He tested if the new sites were actually being backed up.

We hadn't updated 8.4 before that job , and veeam365 now thinks we have all the data.

As for the email notification, this is a 'me-too', since I see others in the thread complaining about the same thing.

[Bubblebop]

I know there are a lot of smart people at Veeam, smarter than me. I've used and sold it since Veeam Backup 2.0.

I think we can tackle this the same way as Crypto Virus; the files have a signature "Sorry, something went wrong", HTML content in non-HTML files is easy to identify and fix.

Then you can scan all new files created in 2026 to reassure everyone.

My own OneDrive files are also corrupted, including the veeam365-usage report over several months.

[Polina]

I'm afraid verification is a bit more complex than that, not to mention fixing the corrupted data.

[Polina]

@Bubblebop

A quickly checked if any contacts from your company were among the recepients of our email communication on KB4835, and found that Case Admin of your account should received our email from April 8th. Other accounts that we used to have on the mailing list unsubscribed from our communications before these communications were sent. If needed, I can share with you emails in DM to verify if those are the correct ones.

I'm sorry for this inconvence and suggest you subscribe to notifications on our KB updates.

[Bubblebop]

Yes, please share in DM

[Bubblebop]

Thanks. Both addresses received the email notice on April 8, and version 8.4 became available on April 27.

The first address doesn’t have the technical ability to notify the rest of us, since it belongs to a license seller. The second address, however, should have been able to act on the notification.

My own address did receive the other notifications, though, and I have not unsubscribed from anything.

Is subscribing to “Get weekly article updates” on the KB the correct way to receive all important updates like this, or is there another recommended notification channel? If possible, could you clarify this for me and for others who may have the same question?

Hope you guys are making progress with the fix

[b.vanhaastrecht]

I only became aware of this issue this week when a customer was unable to restore critical files. Frankly, I'm astonished by the timeline.

The issue has been known since March. A fix for newly created or modified files was released on April 16th, which seems reasonable. What I struggle to understand is why it has now taken more than three months to address the corruption affecting existing, unchanged files during restore operations.

Backup software exists for one primary reason: to ensure that data can be restored when needed. Customers trust Veeam with their business-critical data and pay for that assurance. Given the severity of this issue, it's difficult to understand why there is still no fix available and why support is unable to provide any estimated release date.

Can Veeam provide more transparency on the status of the permanent fix and the expected timeline?

[b.vanhaastrecht]

The latest v8.4 fixes the root cause of the issue, meaning that all backups created after you upgrade to 8.4 will be healthy.

This statement is incorrect. From what support has told me, after installing 8.4 only Changed or Created files will be healthy, non touched files remain corrupted after restore.

[Polina]

The fix delivered in 8.4 is considered permanent.
Remediating the consequences of the issue requires a separate mechanism which is being worked on as we speak. The first phase of it will cover object storage repositories with regular backups. I cannot provide the timeline, but expect to get it delivered soon.

[msobm]

It‘s unbelievable how long it takes for Veeam to get a solution for already corrupted data. That should be one of the highest priority. I don‘t get how that could take (more than) 3 months for such a big company with that much of possible ressources.