Microsoft Security Advisory 3123479

SHA-1 Hashing Algorithm for Microsoft Root Certificate Program

Published: January 12, 2016 | Updated: March 14, 2017

Version: 2.0

Executive Summary

In November of 2016, Microsoft released an update to Internet Explorer and Microsoft Edge that reverted functionality to mark some SHA-1 signed files as untrusted. This change was reverted in the following updates:

  • KB3197869 - November 2016 Preview of Monthly Quality Rollup for Windows 7 SP1 and Windows Server 2008 R2 SP1
  • KB3197875 - November 2016 Preview of Monthly Quality Rollup for Windows 8.1 and Windows Server 2012 R2
  • KB3198585 - Cumulative update for Windows 10: November 8, 2016
  • KB3198586 - Cumulative update for Windows 10 Version 1511: November 8, 2016
  • KB3200970 - Cumulative update for Windows 10 Version 1607 and Windows Server 2016: November 8, 2016

This was done as part of Microsoft’s overall strategy to align our SHA-1 efforts with that of the broader security industry. For more information, please see Windows Enforcement of SHA1 Certificates.

Advisory Details

Issue References

For more information about this issue, see the following references:

References References
General Information Windows Enforcement of SHA1 Certificates
Technical Requirements Protecting Against Weak Cryptographic Algorithms

Suggested Actions

  • Review Microsoft Root Certificate Program Policy Changes
    Customers who are interested in learning more about the topic covered in this advisory should review Windows Enforcement of SHA1 Certificates.

  • Update from SHA-1 to SHA-2
    Certificate authorities should no longer sign newly generated certificates using the SHA-1 hashing algorithm. Customers should instead obtain a SHA-2 certificate from a certificate authority and use that certificate to sign code. To sign code with SHA-2 certificates, see the guidance on this topic at Windows Enforcement of Authenticode Code Signing and Timestamping.

    Impact of action: Older hardware-based solutions may require upgrading to support these newer technologies.

  • Keep Windows Updated
    All Windows users should apply the latest Microsoft security updates to help make sure that their computers are as protected as possible. If you are not sure whether your software is up to date, visit Windows Update, scan your computer for available updates, and install any high-priority updates that are offered to you. If you have Automatic Updates enabled, the updates are delivered to you when they are released, but you have to make sure you install them.

Other Information




The information provided in this advisory is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.


  • V1.0 (January 12, 2016): Advisory published.
  • V2.0 (March 14, 2017): Advisory rereleased to announce that the changes described in this advisory have been reverted as of November 2016. This is an informational change only.

Page generated 2017-03-09 14:08-08:00.