Microsoft security advisory – April 2021 monthly rollup

Number: AV21-157
Date: 13 April 2021

On 13 April 2021 Microsoft published Security Updates to address vulnerabilities in multiple products. Included were critical updates for the following:

  • Windows 10, 8.1, RT 8.1 and 7
  • Windows Server and Server Core
  • Microsoft Azure-related software
  • Microsoft Exchange

Microsoft has indicated that the vulnerabilities fixed in the April 2021 security updates affecting Microsoft Exchange products are different from those previously patched in March 2021. Therefore, running March 2021 security tools and scripts will not mitigate these newly identified vulnerabilities. Microsoft reports that these vulnerabilities, reported by a security partner, have not yet been exploited.

Microsoft recommends that organizations update on-prem servers as soon as possible as Microsoft Exchange Online customers are already protected by the April 2021 security updates.

The Cyber Centre encourages users and administrators to review the provided web links and apply the necessary updates.

April 2021 Release Notes

Security Update Guide

Note to Readers
The Canadian Centre for Cyber Security (Cyber Centre) operates as part of the Communications Security Establishment.  We are Canada’s national authority on cyber security and we lead the government’s response to cyber security events. As Canada's national computer security incident response team, the Cyber Centre works in close collaboration with government departments, critical infrastructure, Canadian businesses and international partners to prepare for, respond to, mitigate, and recover from cyber events. We do this by providing authoritative advice and support, and coordinating information sharing and incident response. The Cyber Centre is outward-facing, welcoming partnerships that help build a stronger, more resilient cyber space in Canada.

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