Microsoft Release Patches for On-Premises Exchange Servers

Microsoft has released patches for multiple on-premises for Microsoft Exchange Server zero-day vulnerabilities that are being exploited by a nation-state affiliated group.

The vulnerabilities exist in on-premises Exchange Servers 2010, 2013, 2016, and 2019. Exchange online is not affected.

To minimise and avoid the impacts of this situation, Microsoft highly recommends that you take immediate action to apply the patches for any on-premises Exchange deployments. Either managed by yourselves or that you are managing for customers. The priority should be servers that are accessible from the internet (e.g. servers publishing Outlook on the web/OAW and ECP).

To patch these vulnerabilities, you should move to the latest Exchange Cumulative Updates and then install the relevant security updates on each Exchange Server.

• You can use the Exchange Server Health Checker script, which can be downloaded from GitHub (use the latest release).
• Running this script will tell you if you are behind on your on-premises Exchange Server updates (note that the script does not support Exchange Server 2010).
• We also recommend that your security team assess whether or not the vulnerabilities were being exploited by using the Indicators of Compromise we shared here.

You can access Microsoft’s Security Update Release relating to this issue here.