An information disclosure vulnerability exists in how Microsoft Exchange validates tokens when handling certain messages. An attacker who successfully exploited the vulnerability could use this to gain further information from a user.
To exploit the vulnerability, an attacker could include specially crafted OWA messages that could be loaded, without warning or filtering, from the attacker-controlled URL. This callback vector provides an information disclosure tactic used in web beacons and other types of tracking systems.
The security update corrects the way that Exchange handles these token validations.
Please be aware that the updates are CU specific. The fact that an update for Exchange 2013 is released indicates the importance of this Security Update.
When installing, start the Security Update from an elevated command prompt (Run As Administrator) and as always, test the security update thoroughly.
Microsoft Exchange Server 2013 Cumulative Update 23
On June 19, 2016 Microsoft released Exchange 2016 CU10 and Exchange 2013 CU21, exactly 90 days after the previous CUs. Perfectly aligned with their regular quarterly release 🙂
Besides regular hotfixes there are a couple of important things to notice:
Exchange 2016 CU10 and Exchange 2013 CU21 need the .NET Framework 4.7.1. This is a hard requirement, so if .NET Framework 4.7.1 is not installed, the setup application will halt and generate an error message. You can use the Get-DotnetVersion.ps1 script that fellow MVP Michel de Rooij wrote to check the .NET version in advance.
A new requirement is the VC++ 2013 runtime library. This component provides WebReady Document Viewing in Exchange Server 2010 and 2013 and Data Loss Prevention in Exchange Server 2013 and 2016. In the (near) future the VC++ 2013 runtime library will be forced to install.
Standard support for Exchange 2013 ended on April 10th, 2018 and thus Exchange 2013 entered extended support. Exchange 2013 CU21 is the last planned CU. Customers need to install this CU to stay in a supported configuration, and to be able to install future Security Releases.
When running a hybrid configuration with Exchange Online, customers are required to install the latest Cumulative Update for Exchange 2013 or Exchange 2016, or install the latest Update Rollup for Exchange 2010 SP3.
None of these releases bring Active Directory Schema changes. You have to run Setup.exe /PrepareAD to activate new features like the following:
A new feature in Exchange 2016 CU10 and Exchange 2013 CU21 is the option to create shared mailboxes in Office 365 using the *-RemoteMailbox cmdlets. For example, after creating a user account in Active Directory you can use the following command to create a Shared Mailbox in Office 365 directly: Enable-RemoteMailbox -Identity <account> -Shared -RemoteRoutingAddress email@example.com
Microsoft also released Update Rollup 22 for Exchange 2010 SP3. This Update Rollup brings support for Windows 2016 Domain Controllers (and corresponding Domain Functional Level and Forest Functional Level) and it fixes an issue with Web Services impersonation.
As always you should thoroughly test the new Cumulative Updates or Update Rollups in your test environment before installing in your production environment.
Installing a Cumulative Update hasn’t changed much over the years, so you can follow my previous blogpost about installing Exchange 2013 CU9, which is especially important when installing a Cumulative Update in a Database Availability Group.
Last week I had to upgrade a few Exchange 2013 CU15 servers to Exchange 2013 CU18. In a typical scenario upgrading to a newer Cumulative Update it’s not a big deal, not even when skipping a few versions, but in this scenario most likely you will hit the following error message:
It fails during the Prerequisite Analysis with the error message
On June 27, 2017 Microsoft has released its quarterly updates for Exchange 2013 and Exchange 2016. The current version is now at Exchange 2013 CU17 and Exchange 2016 CU6. Typically I don’t pay that much attention to this, all new developments seem to be for Office 365 and very little developments for on-premises Exchange deployment. But this time there are some interesting things I’d like to point out.
A couple of days before the release of Exchange 2016 CU6 Microsoft blogged about Sent Items Behavior Control and Original Folder Item Recovery. With the Sent Items Behavior Control, a message that’s sent using the Send As or Send on behalf of permission is not only stored in the mailbox of the user that actually sent the message, but a copy is also stored in the delegator mailbox sent items. This was already possible for shared mailboxes, but now it’s also possible for regular mailboxes (like manager/assistant scenarios).
The Original Folder Item Recovery feature is I guess on of the most requested features. In the past (before Exchange 2010) when items were restored after they were deleted, they were restored to their original location. With the Dumpster 2.0 that was introduced with Exchange 2010 this was no longer possible, and items were restored to the deleted items folder. In this case the items had to be moved manually to their original location. With the introduction of the Original Folder Item Recovery the restore of deleted items again takes place in the original folder.
Customer is running Exchange 2013 with approx. 2500 mailboxes. When looking at calendars and sharing information through the availability service only the availability (free, busy or tentative) is shown. No details are shown by default.
Customer now request to publish more information so that users that want to schedule a meeting can see the details of other user’s appointments. This should not only be configured for existing users, but new users should receive this setting directly when provisioned.
For example, when configuring this for a user called Kim Akers (firstname.lastname@example.org) for all users you can use the following Exchange PowerShell command:
When scheduling a meeting with Kim Akers I can now see her appointment details in Outlook, and I can open the appointment to see all details (read-only) of this appointment as shown in the following two screenshots:
Note. Check the Set-MailboxFolderPermission article on Microsoft TechNet for all details regarding the permissions that can be assigned.