M365 Changelog: Office TLS Certificate Changes

MC343794 – Microsoft 365 is updating services powering messaging, meetings, telephony, voice, and video to use TLS certificates from a different set of Root Certificate Authorities (CAs) due to pending expiration of the Root CA.

Key points:

  • Timing: June 30, 2022
  • Action: Update custom applications that rely on certificate pinning to mitigate interruption in service

How this affects your organization:

The new Root CA “DigiCert Global Root G2” is widely trusted by operating systems including Windows, macOS, Android, and iOS and by browsers such as Microsoft Edge, Chrome, Safari, and Firefox.

Note: Microsoft expects that most Microsoft 365 customers will not be impacted.

However, if you have a custom application, your application may be impacted if it explicitly specifies a list of acceptable CAs. This practice is known as “certificate pinning”. Customers who do not have the new Root CAs in their list of acceptable CAs will receive certificate validation errors, which may impact the availability or function of your application.

  • Affected products include:
    • Microsoft Teams
    • Skype
    • Skype for Business Online
    • GroupMe
    • Kaizala
    • Azure Communication Services
  • Affected endpoints include (but are not limited to):
    • *.teams.microsoft.com
    • *.skype.com
    • *.skypeforbusiness.com
    • *.groupme.com
    • *.communication.azure.com
    • *.operatorconnect.microsoft.com
  • Additionally, Teams and Skype for Business Online endpoints in US Government national cloud instances of Microsoft 365 will make the same change, affecting endpoints such as:
    • *.gcc.teams.microsoft.com
    • *.dod.teams.microsoft.us
    • *.gov.teams.microsoft.us
    • *.online.dod.skypeforbusiness.us
    • *.online.gov.skypeforbusiness.us
    • *.um-dod.office365.us
    • *.um.office365.us

Services began transitioning to the new Root CAs beginning in January 2022 and will continue through October 2022.

What you can do to prepare:
For more details on how to determine if you are affected by this change as well as the details of the new Root CAs, please refer to the technical guidance at Office TLS Certificate Changes.
Additional information