Microsoft has fixed problems affecting its online authentication systems that left a portion of its userbase locked out of multiple cloud-based services unless they were logged in already.
The issues occurred on Monday evening and most customers saw their access restored after Microsoft’s engineers rolled back their systems on early Tuesday morning. According to the Azure status history page, the downtime started approximately at 21:25 UTC on Monday and affected users who were trying to login into services such as Microsoft 365, Azure, and Dynamics 365, as well as into other custom applications that use Azure Active Directory (AAD) authentication.
“Users who were not already authenticated to the cloud services using Azure AD would have seen multiple authentication request failures. Impact was primarily in the Americas based on the issue being exacerbated by load, but users in other regions may also have experienced some impact. Users that had previously authenticated prior to the issue may not have experienced any noticeable effect,” said Microsoft.
In another tweet, the Azure Support account confirmed that both the Azure Public and Azure Government clouds were affected by the issue impacting AAD authentication.
While the results of Microsoft’s in-depth investigation are still a few days away, the company has identified the likely culprits behind the whole situation. The root cause seems to be a combination of three separate and unrelated issues, including a code defect in a service update, a tooling error in the Azure AD safe deployment system, and a code defect in Azure AD’s rollback mechanism.