Despite the quarterly wave of Cumulative Updates being imminent, CVE-2017-11932 and ADV170023 warranted a quick release of Security Update KB4045655 for current versions of Exchange 2013 and Exchange 2016.
This security update fixes a vulnerability in OWA, which could allow elevation of privilege or spoofing if an attacker sends an email that has a specially crafted attachment to a vulnerable Exchange server.
You can download the security updates here:
Be advised the update may leave your Exchange services in a disabled state, despite installing correctly. In those cases, reconfigure those services to Automatic and start them manually.
Also note that this security update overrides an earlier update, KB4036108, which might cause Calendar Sharing issues when split DNS is used.
Security updates are Cumulative Update level specific. Be advised that updates may carry the same name, e.g. the update for CU7 and the one for CU6 are both Exchange2016-KB4045655-x64-en.msp. I suggest adding some form of Cumulative Update identification to the file name when archiving it, e.g. Exchange2016-KB4045655-x64-en-CU7.msp.
As with any patch or update, I’d recommend to thoroughly test this in a test and acceptance environment first, prior to implementing it in production.
Honeymoon caused some backlog, and one of the things to post was that the Exchange Team released the September updates for Exchange Server 2013 and 2016. Like the previous Cumulative Updates for these Exchange versions, Exchange 2013 CU18 and Exchange 2016 CU7 require .NET Framework 4.6.2; NET Framework 4.7.1 is currently being tested (4.7 will be skipped), and support for 4.7.1 is expected for the December updates.
Exchange 2016 CU7 fixes:
Exchange 2013 CU18 fixes:
- KB4040755 New health monitoring mailbox for databases is created when Health Manager Service is restarted in Exchange Server 2013
- KB4040121 You receive a corrupted attachment if email is sent from Outlook that connects to Exchange Server in cache mode
- KB4040120 Synchronization may fail when you use the OAuth protocol for authorization through EAS in Exchange Server 2013
- KB4036108 Security update for Microsoft Exchange: September 12, 2017
- Exchange 2016 CU7 requires Forest Functionality Level 2008R2 or later.
- Exchange 2016 CU7 includes schema changes, but Exchange 2013 CU18 does not. However, Exchange 2013 CU17 may introduce RBAC changes in your environment. Where applicable, use setup /PrepareSchema to update the schema or /PrepareAD to apply RBAC changes, before deploying or updating Exchange servers. To verify this step has been performed, consult the Exchange schema overview.
- When upgrading your Exchange 2013 or 2016 installation, don’t forget to put the server in maintenance mode when required. Regardless, setup will put the server in server-wide offline mode post-analysis, before making actual changes.
- Using Windows Management Framework (WMF)/PowerShell version 5 or later on anything earlier than Windows Server 2016 is not supported. Don’t install WMF5 on your Exchange servers running on Windows Server 2012 R2 or earlier.
- NET Framework 4.7.1 is being tested by the Exchange Team, but .NET Framework 4.7.1 nor .NET Framework 4.7 are supported.
- When using Exchange hybrid deployments or Exchange Online Archiving (EOA), you are required to stay at most one version behind (n-1).
- If you want to speed up the update process for systems without internet access, you can follow the procedure described here to disable publisher’s certificate revocation checking.
- Cumulative Updates can be installed directly, i.e. no need to install RTM prior to installing Cumulative Updates.
- Once installed, you can’t uninstall a Cumulative Update nor any of the installed Exchange server roles.
- The order in which you upgrade servers with Cumulative Updates is irrelevant.
Caution: As for any update, I recommend to thoroughly test updates in a test environment prior to implementing them in production. When you lack such facilities, hold out a few days and monitor the comments on the original publication or forums for any issues.