Cohesity - Remediation-M365 Azure ACS Retirement

Cohesity - Remediation - M365 Azure ACS Retirement

Introduction

Microsoft will be retiring its ACS (Access Control of Services) for M365 on April 2, 2026. This will directly affect Cohesity M365 source registrations as those configurations leverage ACS through App Secret Key. As an alternative, Cohesity will support using certificate-based authentication (CBA) for access for M365 sources moving forward.

Purpose

This document will provide clients illustrations and steps on how to migrate your M365 sources from ACS to CBA at the client’s convenience. Please note, that this migration must be completed before April 2, 2026 or backups and/or restores will be impacted due to lack of access.

Cohesity - Verifying Microsoft Azure App ID

	Log into the Cohesity cluster that contains the M365 source. Review the illustration to navigate to edit the M365 settings.
	Navigate to the Azure Applications and take note of the App ID. This can be used to cross reference the appropriate Azure App that needs to be updated with a Cohesity generated public certificate.

Microsoft Azure App - Uploading Cohesity Certificate

	Navigate into Microsoft Azure and navigate to the App dedicated for Cohesity (please refer to the App ID to confirm the correct Azure App). Once in the app, navigate to Upload certificate and upload the .cert provided to you by the Expedient OSC.
	Take note of the certificate thumbprint as seen in the illustration for updating the Cohesity source. This can also be cross-referenced in the Expedient SMC ticket that the correct certificate was provided by the OSC.

Cohesity - Updating the M365 Source To Use the Azure App Certificate

Log into the Cohesity cluster that contains the M365 source. Review the illustration to navigate to edit the M365 settings.

Navigate to the Azure Applications and locate the appropriate App ID. Use the drop down and search bar to reference the thumbprint or Azure App name to be used for the source. Click Update to apply settings.

Please be aware that Cohesity will attempt to verify authenticating when applying the source settings. If there are any issues, Cohesity will fail the update.