An industry-wide, hardware-based security vulnerability was disclosed today. Keeping customers secure is always our top priority and we are taking active steps to ensure that no Azure customer is exposed to these vulnerabilities. At the time of this blog post, Microsoft has not received any information to indicate that these vulnerabilities have been used to attack Azure customers.

With the public disclosure of the security vulnerability today, we are accelerating the planned maintenance timing and will begin automatically rebooting the remaining impacted VMs starting at 3:30pm PST on January 3, 2018. The self-service maintenance window that was available for some customers has now ended, in order to begin this accelerated update.

The majority of Azure customers should not see a noticeable performance impact with this update.