During backup operations, files, list attachments, or images from SharePoint, OneDrive, or Teams were saved with the contents of the HTML error pages returned by the API, rather than their actual file content.
Veeam first observed this issue in early March 2026.
This issue impacts Veeam Data Cloud for Microsoft 365 and all supported versions of Veeam Backup for Microsoft 365. It is independent of repository type, affecting both JET-based and object storage repositories.
No errors are shown in backup jobs or restore tasks; the issue surfaces only when the user attempts to open the restored file.
I'm lost for words.
Is there a way to verify the extent of how many Tenants/Services/Files are affected? Are they backups even usable at this stage?
The issue is observed on some of the files, and otherwise the current backups remain usable.
First hand we are preparting a fix for the root cause - it's now undergoing the last tests. Verification and remediation of the impact (whereas possible) will be a fast-follow.
Btw, you can subscribe for Veeam's KBs updates to get notified once the new content is out.
As others are asking, in the meantime is there any way of determining which backed up documents are impacted ? What's the scope of the problem ? There's no update on https://www.veeam.com/kb4835.