EX257883: Admins may be unable to access the Exchange admin center

An expired certificate is stopping some admins from accessing the Exchange admin center at Admin.Exchange.Microsoft.com.

Some browsers, like Chrome, are blocking the site completely, while others such as Firefox let you enter with a warning.

The issue appears to have been going on for the last 7-8 hours, with Microsoft trying to roll out a fix.

We've isolated the problem and are applying a fix. Additional details can be found in the Service health dashboard under EX257883.

— Microsoft 365 Status (@MSFT365Status) May 23, 2021

The certificate expired today, Sun, 23 May 2021, at 12:00:00 UTC. For those on the east coast of the United States, that is is equivalent to Sun, 23 May 2021 08:00:00 EST.

Microsoft writes:

We’re continuing to work on applying a configuration fix on the affected authentication component, which we expect will fully mitigate impact. Although our current estimate for completing this configuration change is within the next five and a half hours, we’re assessing our options to expedite a resolution.

Microsoft says one workaround is to access the portal via https://outlook.office.com/ecp/.

Microsoft appears close to resolving the issue. Affected admins can follow the progress of the issue under the EX257883 advisory.

via BleepingComputer.