Tuesday, April 13, 2021

Microsoft April 2021 Security Updates

The Microsoft April 2021 security updates have been released and consist of 114 CVEs.  The updates apply to the long list of products, features and roles that can be found in the April Security Updates Guide.  Of these 89 CVEs, 19 are rated Critical, 89, and 1 is rated Important in severity. Six additional bugs impact Chromium-based Edge.  


According to Microsoft, one bug is currently being exploited while four others are publicly known at the time of release.  In addition, CVE-2021-28310 is listed as being actively exploited.


The  updates released today will automatically remove Edge Legacy which is out of support and replace it with the new Chromium-based Edge.  In the event you still use legacy Edge or if you have blocked the Chromium Edge update using group policies/registry hacks, those settings will be ignored and the legacy version will be removed automatically.


Important Note For Windows 10, Version 2004 and Windows 10, Version 20H2:

Before installing this update

Prerequisite:  Microsoft now combines the latest servicing stack update (SSU) for your operating system with the latest cumulative update (LCU). If you encounter the error, 0x800f0823 – CBS_E_NEW_SERVICING_STACK_REQUIRED, close the error message and install the last standalone SSU (KB4598481) before installing this LCU. You will not need to install this SSU (KB4598481) again for future updates. 


For general information about SSUs, see Servicing stack updates and Servicing Stack Updates (SSU): Frequently Asked Questions.


For Windows 10 Version 1909, see KB5001337.


The KBs listed below contain information about known issues with the security updates:

KB Article

Applies To


SharePoint Server 2019 Language Pack


SharePoint Server 2019


Windows 10, Version 2004, Windows Server, Version 2004, Windows 10, Version 20H2, Windows Server, Version 20H2


Windows Server 2008 (Security-only update)


Windows 7, Windows Server 2008 R2 (Monthly Rollup)


Windows 10, Version 1909, Windows Server, Version 1909


Windows 10, Version 1809, Windows Server 2019


Windows 10, Version 1607, Windows Server 2016


Windows 8.1, Windows RT 8.1, Windows Server 2012 R2 (Monthly Rollup)


Windows Server 2012 (Security-only update)


Windows Server 2012 (Monthly Rollup)


Windows Server 2008 (Monthly Rollup)


Windows 7, Windows Server 2008 R2 (Security-only update)


Windows 8.1, Windows RT 8.1, Windows Server 2012 R2 (Security-only update)


Microosft Exchange Server 2019, 2016, 2013


 Recommended Reading:   See Dustin Childs review and analysis in Zero Day Initiative -- TheApril 2021 Security Update Review.


Additional Update Notes:



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