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March 2021 Exchange Server Security Updates

Microsoft released several Security Updates (SUs) for Microsoft Exchange Server to address vulnerabilities that have been used in limited targeted attacks. Due to the critical nature of these vulnerabilities, we recommend that customers apply the updates to affected systems immediately to protect against these exploits and to prevent future abuse across the ecosystem.

These vulnerabilities affect Microsoft Exchange Server. Exchange Online is not affected.

Exchange Server Security Updates

Microsoft has released a set of out of band Security Updates for vulnerabilities for the following versions of Exchange Server:

  • Exchange Server 2013
  • Exchange Server 2016
  • Exchange Server 2019

Security Updates are available for the following specific versions of Exchange:

Read more on how to Install Exchange Security Update.

If you are not at these Exchange Server CU versions, please update right now and apply the above patch.

Read more on how to Install Cumulative Update Exchange.

These vulnerabilities are used as part of an attack chain. The initial attack requires the ability to make an untrusted connection to Exchange server port 443. This can be protected against by restricting untrusted connections, or by setting up a VPN to separate the Exchange server from external access. Using this mitigation will only protect against the initial portion of the attack; other portions of the chain can be triggered if an attacker already has access or can convince an administrator to run a malicious file.

We recommend prioritizing installing updates on Exchange Servers that are externally facing. All affected Exchange Servers should ultimately be updated.

FAQs

My organization is in Hybrid mode with Exchange Online. Do I need to do anything?
While Exchange Online customers are already protected, the October 2021 security updates do need to be applied to your on-premises Exchange Servers, even if they are used only for management purposes. You do not need to re-run the Hybrid Configuration Wizard (HCW) after applying updates.

Do I need to install the updates on “Exchange Management Tools only” workstations?
Servers or workstations running only Microsoft Exchange Management Tools (no Exchange services) do not need to apply these updates.

Further information

ALI TAJRAN

ALI TAJRAN

ALI TAJRAN is a passionate IT Architect, IT Consultant, and Microsoft Certified Trainer. He started Information Technology at a very young age, and his goal is to teach and inspire others. Read more »

This Post Has One Comment

  1. Hi Ali,

    You wrote this in an earlier article: “These vulnerabilities are used as part of an attack chain. The initial attack requires the ability to make an untrusted connection to Exchange server port 443. This can be protected against by restricting untrusted connections, or by setting up a VPN to separate the Exchange server from external access.”

    Is it recommended to use vpn even after the upgrade? In many cases, using vpn makes it difficult for users to connect.

    thanks, John

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