Microsoft Office version 2609 & CDM breaking change

Work over the weekend has identified that the issue has been resolved without intervention to CDM.

No update to MS Office or changes to CDM are required. We believe a follow up backend fix from Microsoft has caused this behaviour. The incident is therefore considered closed; we will continue to monitor fix stability next week.

Microsoft Office & CDM breaking change:
We are aware that the latest version of MS Office, released 22nd September contains a breaking change to CDM which could cause work to be lost.

Source:
Version 2609 , build 20430.20092 was released 22nd September 2026 via Current Channel updates and contains a version of MS Word which does not allow files to be saved correctly through Cloud Drive Mapper.

Behaviour:
The following workflows are potentially impacted:
• Opening a Word document from a mapped drive and using Save As
• Creating a document locally and saving it to a mapped drive
• Using Save a Copy to a mapped drive

Recommendation:
Customers who have not yet updated Microsoft Office to Version 2609 (Build 20430.20092) should prevent or defer deployment of this Office build to devices using Cloud Drive Mapper.
Customers who have already updated to the affected Office build should roll Microsoft 365 Apps back to the previous build (Version 2608 (Build 20326.20158)) and prevent Office from automatically updating to Version 2609 while the issue is being investigated.

Fix:
We have raised a Bug which our development teams are working on as a priority. We will provide an update once investigations have concluded as to how we will address the issue.

Update 24th Sept:
We have been able to reproduce the issue internally and are now working to identify root cause. Investigations continue as a priority.

Microsoft release notes for Office are here:
https://learn.microsoft.com/en-us/officeupdates/current-channel