Exchange Updates (and more) – H1 2023

Posted on May 4, 2023 by Michel de Rooij

The Exchange Team released Exchange Server 2019 Cumulative Update H1 2023, or CU13. This is Exchange 2019 only; no Exchange 2016 CU.

Apart from the fixes, this Cumulative Update for Exchange 2019 contains the following functionality enhancements:

Modern Authentication On-Premises Support
After dropping support for Basic Authentication in Exchange Online, organizations that remained on-premises for various reasons, and could not deploy Exchange Hybrid, were left out in doubt how to proceed. Last year, Microsoft gave them some perspective, following a roadmap announcement.

This CU is a first step, allowing organizations running AD FS 2019 to deploy Exchange 2019 CU13, and configure AD FS as their authentication provider. Be advised that this also requires clients to support this change in authentication logic. First, Outlook for Windows will contain support for this in build 16327.20200 and later. Support for other Outlook clients has an ETA of end of year. Outlook on the Web already supports claims-based authentication using AD FS, which is a form of Modern Authentication.

Finally, organization running Exchange 2016 can deploy Exchange 2019 CU13 in front of those Exchange 2016 servers, allowing then to handle clients request, and thus authenticate them using AD FS. After deployment, organizations can enable Modern Authentication on the organization or at the mailbox level, using Exchange’s Authentication Policies.

For more information about deploying Modern Authentication with Exchange on-premises, see Enabling Modern Auth in Exchange On-Premises. The page also includes an insightful diagram on the authentication flow.

Configuration Backup/Restore
Administrators might tweak configuration files belonging to their Exchange deployment, e.g. web.config. Deploying CUs meant that those files were overwritten, and administrators had to re-apply changes. With CU13, setup will now preserve a fixed set of elements in those configuration files. For more information, see Exchange Server custom configuration preservation.

TLS 1.3
Unfortunately, nothing yet about TLS 1.3 support.

Earlier Exchange Versions
Exchange 2013 reached end of life early April. No Cumulative Update for Exchange 2016 CU23, which is in extended support, and will only receive security updates until October, 2025. Exchange 2016 is supported when you run CU23 with the March 2023 Security Update applied.

Download
Link to the update as well as a description of changes and fixes are below. The column Schema and AD indicate if the CU contains Schema (/PrepareSchema) and Active Directory (PrepareAD) changes compared to the previous CU. Refer to the Exchange Schema page for schema and related versioning information. Also, in order to be able to manage Modern Authentication, administrators need to explicitly run /PrepareAD.

Version	Build	KB	Download	UMLP	Schema	AD
Exchange 2019 CU13	15.2.1258.12	KB5020999	Download		N	Y

Exchange 2019 CU13 fixes:

5027150 Enable Modern Auth for pure On-Premises Exchange users
5026134 “InvalidRecipientsException” when you try to run MRM
5026135 CertificateDeploymentServicelet failure in multiple domain forest Exchange deployments
5026136 Microsoft Exchange Transport doesn’t re-encrypt IRM messages
5026138 Users receive reminders although the meeting reminder is set to None
5026139 You can’t move the public folder mailbox
5026142 Journal message returns “ConversionFailedException”
5026143 OAB shadow distribution threshold must be reduced or made configurable
5026146 Expiry notification is sent to moderator and sender for approved and delivered messages
5026147 BlockLegacyAuthentication fail Organization Policy because of BackendRehydrationModule implementation
5026149 Group metrics generation doesn’t finish in multidomain environment
5026150 Edge server Filtering Agent removes journal attachments
5026151 Oab-Processing-Threshold is set to 0 for On-Premises
5026152 Microsoft Exchange ActiveSync or Current Requests counter inaccurately counts requests
5026153 Delivery Flow Control setting override is now available
5026154 On-premises Exchange has 35MB file size limit for online archiving
5026155 “No support for this operation” error on an Exchange 2019 DAG member server
5026156 Outlook search fails in a shared On-Premises mailbox if the primary user mailbox is migrated to Exchange Online
5026158 The body of recurring meeting is not clear if it has Chinese characters
5026159 IconIndex returns Default value when Server Assisted Search is used in Outlook
5026266 “Could not start MS Exchange Service Host service” error and Exchange stops responding
5026267 OWA stops responding in an Exchange 2019 and 2016 coexistence topology
5026268 Store Worker process crashes and returns “System.NullReferenceExceptions” multiple times per day
5026269 Block deserialization error when using eDiscovery
5026271 IIS URL Rewrite Module link is incorrect
5026273 Outlook configuration fails in Android or iOS
5026274 Hybrid Agent Validation fails after Extended Protection is enabled
5026277 Mail configuration fails on iOS device after Extended Protection is enabled
5026278 Mailbox migration fails after Extended Protection is enabled

Notes

If Cumulative Updates contain schema changes compared to the Cumulative Update you currently have deployed, you need to run Setup with /PrepareSchema. If they contain Active Directory changes, you need to run /PrepareAD. Alternatively, permissions permitting, you can let Setup perform this step. Consult the Exchange schema versions page for schema and related versioning information.
When upgrading from an n-2 or earlier version of Exchange, or an early version of the .NET Framework, consult Upgrade Paths for CU’s & .NET.
Don’t forget to put the Exchange server in maintenance mode prior to updating. Regardless, setup will put the server in server-wide offline mode post-analysis, before making actual changes.
When using Exchange hybrid deployments or Exchange Online Archiving (EOA), support requires you to trail at most one version (n-1).
Ensure the Windows PowerShell Script Execution Policy is set to Unrestricted during deployment. This to prevent installation failures due to inability to validate script signatures.
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; no need to install RTM prior to installing Cumulative Updates.
Once upgraded, you can’t uninstall a Cumulative Update nor any of the installed Exchange server roles.
The recommended upgrade order is internet-facing, non-internet-facing servers first, followed by Edge Transports.

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.

Teams Calendar View in Apple CarPlay

Posted on March 30, 2023 by Michel de Rooij

A small post on something that I only noticed today, which is that one of the recent updates for the Teams app on iOS introduced the much welcome support for Calendar View in Teams on CarPlay. This was published since January as Roadmap ID 114306 and is also published in the Message Center as MC516905. I am currently running Teams for iOS version 5.5.0, so that build definitely contains this functionality.

No longer you need to tell Siri you want to join your ‘next meeting’, as you now will be presented with current and upcoming events. You can join any meetings early simply by tapping on them, and joinable meetings will display a phone icon, which you can also tap to join. Of course, you can only join Teams meetings, if you tap a regular appointment you will get a notice that this is not a Teams meeting.

The picture below shows the Calendar View both on Teams Mobile (left) and the corresponding view as displayed on Teams for iOS with CarPlay (right). It shows our Test meeting which is currently in progress, as indicated by a progress bar as well.

Note that the calendar view is showing today’s items, and only from the currently active account in Teams Mobile on your connected mobile device. If you have multiple accounts configured, switching accounts on Teams Mobile is required to show their respective calendars. Doing so will update the Calendar View immediately and allows you to join those meetings using the display. A holistic view would be nice, but compared to where Teams on CarPlay is coming from, this is already a big step in usability.

A small request to the Teams development group: Please use meaningful descriptions to the version history, as this added functionality is nowhere to be found between the “Bug fixes and performance improvements” and occasional mention of functionality changes.

Security Updates Exchange 2013-2019 (Mar2023)

Posted on March 14, 2023 by Michel de Rooij

The Exchange product group released March updates for Exchange Server 2013, 2016 and 2019. Be advised that the Exchange team also put out a notice for fixed vulnerability in Outlook (CVE-2023-23397), together with a supporting script to analyze mailboxes for this possible exploit (link), which is rather uncommon.

The vulnerability addressed in these Security Updates for Exchange Server is:

Vulnerability	Category	Severity	Rating
CVE-2022-21978	Remote Code Execution	Important	CVSS:3.1 8.8 / 7.7

The Security Updates for each supported Exchange Server build are linked below:

Exchange	Download	Build	KB	Supersedes
Exchange 2019 CU12	Download	15.2.1118.26	KB5024296	KB5023038
Exchange 2019 CU11	Download	15.2.986.42	KB5024296	KB5023038
Exchange 2016 CU23	Download	15.1.2507.23	KB5024296	KB5023038
Exchange 2013 CU23	Download	15.0.1497.48	KB5024296	KB5023038

Note: As mentioned last month, be advised that Exchange Server 2013 support will end in April, 2023. This means: Exchange 2013 will stop to receive security updates. Recommendation is to upgrade to a more recent version, or move to Exchange Online.

Other Issues
Apart from security fixes, these SUs also fix the following:

Issue	Exchange 2013	Exchange 2016	Exchange 2019
You can’t access Toolbox on Exchange after enabling EnableSerializationDataSigning	Yes	Yes	Yes
EEMS stops responding after TLS endpoint certificate update	Yes	Yes	Yes
Get-App and GetAppManifests fail and return an exception	Yes	Yes	Yes
EWS does not respond and returns an exception	Yes	Yes	Yes
An exception is returned while opening a template in the Exchange Toolbox	Yes	Yes	Yes

Notes:

Security updates are Cumulative Update level specific. You cannot apply the update for Exchange 2019 CU12 to Exchange 2019 CU11. When downloading, the security update will carry the same name for different Cumulative Updates, and I would suggest tagging the file name with the CU level when archiving it, e.g. Exchange2019-CU12-KBXXXXXX-x64-en.msp.
Similar to Cumulative Updates, Security Updates are cumulative and you only need to install the latest SU for your CU.
Exchange servers running as part of hybrid deployment are managed through PowerShell, and thus need to be receive this patch and eventually be enabled for payload signing.
If you have installed the Exchange Management Tools separately for managing your on-premises Exchange Servers, or installed it after removal of the Last Exchange Server for recipient management, it is recommended to apply the Security Update.

On a final note, as with any patch or update, I’d recommend to apply this in a test environment first, prior to implementing it in production. However, it is not recommended to wait for regular maintenance cycles when it concerns security updates, and follow a more agile approach; the ratings are an indication of the urgency.

Security Updates Exchange 2013-2019 (Feb2023)

Posted on February 15, 2023 by Michel de Rooij

[20Feb] Added information regarding issues reported.

The Exchange product group released February updates for Exchange Server 2013, 2016 and 2019.

The vulnerabilities addressed in these Security Updates are:

Vulnerability	Category	Severity	Rating
CVE-2023-21529	Remote Code Execution	Important	CVSS:3.1 8.8 / 7.7
CVE-2023-21706	Remote Code Execution	Important	CVSS:3.1 8.8 / 7.7
CVE-2023-21707	Remote Code Execution	Important	CVSS:3.1 8.8 / 7.7
CVE-2023-21710	Remote Code Execution	Important	CVSS:3.1 7.2 / 6.3

The Security Updates for each supported Exchange Server build are linked below:

Exchange	Download	Build	KB	Supersedes
Exchange 2019 CU12	Download	15.2.1118.25	KB5023038	KB5022193
Exchange 2019 CU11	Download	15.2.986.41	KB5023038	KB5022193
Exchange 2016 CU23	Download	15.1.2507.21	KB5023038	KB5022143
Exchange 2013 CU23	Download	15.0.1497.47	KB5023038	KB5022188

Other Issues
Apart from security fixes, these SUs also fix the following:

Issue	Exchange 2013	Exchange 2016	Exchange 2019
Export-UMPrompt fails with InvalidResponseException	Yes	Yes	N/A
Edge Transport service returns an “EseNtOutOfSessions” Exception	Yes	Yes	Yes
Exchange services in automatic startup mode do not start automatically	Yes	Yes	Yes
Data source returns incorrect checkpoint depth	Yes	Yes	Yes
Serialization fails while tried accessing Mailbox Searches in ECP	Yes	Yes	Yes
Transport delivery service mishandles iCAL events	Yes	Yes	Yes

Notes:

Security updates are Cumulative Update level specific. You cannot apply the update for Exchange 2019 CU12 to Exchange 2019 CU11. When downloading, the security update will carry the same name for different Cumulative Updates, and I would suggest tagging the file name with the CU level when archiving it, e.g. Exchange2019-CU12-KBXXXXXX-x64-en.msp.
Similar to Cumulative Updates, Security Updates are cumulative and you only need to install the latest SU for your CU.
Exchange servers running as part of hybrid deployment are managed through PowerShell, and thus need to be receive this patch and eventually be enabled for payload signing.
If you have installed the Exchange Management Tools separately for managing your on-premises Exchange Servers, or installed it after removal of the Last Exchange Server for recipient management, it is recommended to apply the Security Update.

[20Feb] Shortly after release, people reported through the comments that EWS started having issues after deploying the security update. Symptoms reported were problems with (server side) searches, add-ins not loading, and calendar operations such as scheduling or sharing taking a long time to load. Since it’s EWS having problems, applications depending on this protocol also may stop to work, such as Teams.

Meanwhile, Microsoft acknowledged an issue with the initial publication, and published workaround. If experience issues and see the event 4999 in your Eventlog:

E12IIS, c-RTL-AMD64, 15.01.2507.021, w3wp#MSExchangeServicesAppPool, M.Exchange.Diagnostics, M.E.D.ChainedSerializationBinder.EnforceBlockReason, M.E.Diagnostics.BlockedDeserializeTypeException, 437c-dumptidset, 15.01.2507.021.

follow the instructions in the following KB article link:

On each Exchange server, create a registry key
New-ItemProperty -Path HKLM:\SOFTWARE\Microsoft\ExchangeServer\v15\Diagnostics -Name 'DisableBaseTypeCheckForDeserialization' -Value 1 -Type String
Create a global override setting
New-SettingOverride -Name 'Adding learning location ClientExtensionCollectionFormatter' -Component Data -Section DeserializationBinderSettings -Parameters @('LearningLocations=ClientExtensionCollectionFormatter') -Reason 'Deserialization failed'
If you cannot wait until the override configuration kicks in (may take an one hour), refresh it manually:
- Get-ExchangeDiagnosticInfo -Process Microsoft.Exchange.Directory.TopologyService -Component VariantConfiguration -Argument Refresh
- Restart IIS and the Windows Activation Proces on each server
  Restart-Service -Name W3SVC, WAS -Force

Be advised that event 4999 might still show up in your Eventlog, and it has been reported that this might not completely does away with the issues reported. Keep an eye on the original post and EHLO blog for any future updates.

Security Updates Exchange 2013-2019 (Jan2023)

Posted on January 10, 2023 by Michel de Rooij

The Exchange product group released January updates for Exchange Server 2013, 2016 and 2019.

The vulnerabilities addressed in these Security Updates are:

Vulnerability	Category	Severity	Rating
CVE-2023-21764	Elevation of Privilege	Important	CVSS:3.1 7.8 / 6.8
CVE-2023-21763	Elevation of Privilege	Important	CVSS:3.1 7.8 / 6.8
CVE-2023-21745	Spoofing	Important	CVSS:3.1 8.8 / 7.9
CVE-2023-21762	Spoofing	Important	CVSS:3.1 8.0 / 7.0
CVE-2023-21761	Information Disclosure	Important	CVSS:3.1 7.5 / 6.5

The Security Updates for each Exchange Server version are linked below. Note that only CVE-2023-21762 applies to Exchange Server 2013:

Exchange	Download	Build	KB	Supersedes
Exchange 2019 CU12	Download	15.2.1118.21	KB5022193	KB5019758
Exchange 2019 CU11	Download	15.2.986.37	KB5022193	KB5019758
Exchange 2016 CU23	Download	15.1.2507.17	KB5022143	KB5019758
Exchange 2013 CU23	Download	15.0.1497.45	KB5022188	KB5019758

In case you are wondering why Exchange Server 2016 CU22 is not mentioned: CU22 went out of support, and only CU23 will continue to receive security updates. On another note, Exchange 2013 support will end in April, 2023, meaning it it will stop receiving security updates. Recommendation is to upgrade to a more recent version.

Payload Serialization Signing
Apart from fixing security issues, these SUs also introduce support for certificate-based signing of PowerShell serialization payloads. TLDR; it allows for signing data to identify possible tampering. More info on the topic here. The process is explained at https://aka.ms/HC-SerializedDataSigning. In order to verify or configure signing, a script has been published here, or check here if you prefer manual steps. Note that all your Exchange servers need to run this SU before you enable signing, as each Exchange server needs to understand the signing.

Other Issues
Apart from security fixes, these SUs also fix the following:

Issue	Ex2013	Ex2016	Ex2019
Store Worker Process stops and returns “System.NullReferenceExceptions” multiple times per day		Yes	Yes
Can’t record or play in Exchange Unified Messaging	Yes	Yes
Exchange Application log is flooded with Event ID 6010		Yes

Security updates are Cumulative Update level specific. You cannot apply the update for Exchange 2019 CU12 to Exchange 2019 CU11. When downloading, the security update will carry the same name for different Cumulative Updates, and I would suggest tagging the file name with the CU level when archiving it, e.g. Exchange2019-CU12-KBXXXXXX-x64-en.msp.

Exchange servers running as part of hybrid deployment are managed through PowerShell, and thus need to be receive this patch and eventually be enabled for payload signing. If you are running Exchange 2019 Management Tools-only (for recipient management), you do not need to deploy this SU.

Security Updates Exchange 2013-2019 (Nov2022)

Posted on November 8, 2022 by Michel de Rooij

The Exchange product group released November updates for Exchange Server 2013, 2016 and 2019. Note that these Security Updates address the vulnerabilities CVE-2022-41040 and CVE-2022-41082 that were reported end of September. More on those in an earlier post.

Note: You can keep the current URLScan mitigations in-place, and remove them after installing these security updates at your convenience. The recommendation to disable Remote PowerShell for non-admins is upheld, but this is best practice regardless.

The vulnerabilities addressed in these Security Updates are:

Vulnerability	Category	Severity	Rating
CVE-2022-41040	Elevation of Privilege	Critical	CVSS:3.1 8.8 / 7.9
CVE-2022-41082	Elevation of Privilege	Important	CVSS:3.1 8.8 / 8.3
CVE-2022-41078	Elevation of Privilege	Important	CVSS:3.1 8.0 / 7.0
CVE-2022-41123	Elevation of Privilege	Important	CVSS:3.1 7.8 / 6.8
CVE-2022-41079	Elevation of Privilege	Important	CVSS:3.1 8.0 / 7.0
CVE-2022-41080	Elevation of Privilege	Critical	CVSS:3.1 8.8 / 7.7

The following Security Updates address these vulnerability for the Exchange builds mentioned, with the exception of CVE-2022-41123 which does not apply to Exchange Server 2013:

Exchange	Download	Build	KB	Supersedes
Exchange 2019 CU12	Download	15.2.1118.20	KB5019758	KB5019077
Exchange 2019 CU11	Download	15.2.986.36	KB5019758	KB5019077
Exchange 2016 CU23	Download	15.1.2507.16	KB5019758	KB5019077
Exchange 2016 CU22	Download	15.1.2375.37	KB5019758	KB5019077
Exchange 2013 CU23	Download	15.0.1497.44	KB5019758	KB5019076

In case you missed it, per the Security Updates of August, you can enable Windows Extended Protection for increased protection against certain vulnerabilities. More information this process and its requirements can be found in the post on the August updates here.

Security updates are Cumulative Update level specific. You cannot apply the update for Exchange 2019 CU12 to Exchange 2019 CU11. Also, the security update download has the same name for different Cumulative Updates, and I would suggest tagging the file name with the CU level, e.g. Exchange2019-CU12-KBXXXXXX-x64-en.msp.

Exchange servers running as part of hybrid deployment are running services, and thus need to be included in the patch cycle. If you are running Exchange 2019 CU12 Management Tools-only (for recipient management), you do not need to deploy this SU.

Using PowerAutomate to echo tweets on Mastodon

Posted on November 7, 2022 by Michel de Rooij

November 22nd, 2022: Updated Flow diagram and updated blog to mention usage of vars for Mastodon host and bearer token.

And now for something completely different: With the recent news around Twitter, many people are having a look at alternatives. One of these is Mastodon, which is an open source platform, using federated identities on a distributed network. In essence, this means there is not a single phone directory but multiple, yet people living in different phone books can interact with each other as if they were residing in one (federation). Only thing is that, apart from your handle, you also need to know your (Mastodon) host where your account lives.

Now, this isn’t a blog on this social media platform, but it is a quick introduction on how to enable API access to your Mastodon account, and how you can leverage that in PowerAutomate. You can then, for example, toot your tweets (on Mastodon, one toots). There is no built-in action for Mastodon in PowerAutomate, so we need to create it leveraging Mastodon’s API, which is fairly simple for this action.

To start, you need a registered Mastodon account as well as PowerAutomate. First, we are going to configure your account in Mastodon for API access by an app. Navigate to Preferences, select </> Development and Click New Application. You now need to enter some details about your application, such as name and site where the calls originate from, e.g.

Application Name: PowerAutoMate
Application Website: https://make.powerautomate.com

The Redirect URI field can be left at its default.

At the bottom of the dialog , you need to specify which calls your application is allowed to make by means of Scopes. For this example, we will only post status updates, so we deselect anything checked, and check write:statuses, which will allow us to post status updates. Click Submit.

After submitting, return to your App details page, and you will notice at the top there is now a client key and secret assigned to the app, as well as an access token. This access token is something we need later on, so make note of it or keep the screen open.

Disclaimer: The Premium connector HTTP is used, which might require a covering Per Flow or Per User service plan. When you don’t, you will get a message during import stating that you “do not have a service plan adequate for the non-standard connection”.

In PowerAutomate, import the Flow package TootMyTweet that I published on GitHub here. During import, pick your Twitter connection to use. After importing, You need to edit the flow by choosing Edit, and make the customizations indicated below the overview diagram:

In the When a new tweet is posted trigger, change <Your Twitter Handle> in the query to your Twitter handle (or replace with any other query you desire).
In the step Initialize MastodonInstance variable, change the value to your Mastodon host, e.g. mastodon.social.
In the step Initialize AuthorizationToken variable, change the value to the Access Token you wrote down earlier from the Mastodon app configuration.
The body sets the status field to the tweet, after escaping quotes and expanding any URLs shortened by Twitter. For status (and other) API call information, see the Mastodon documentation here.
Note that replies are ignored, as context is lost when tooting replies to Tweets.

Save these changes, and do not forget to enable the Flow. Then wait for the first tweet to be automatically echoed on Mastodon.

Note that this of course is far from perfect: We will skip tooting replies (that is what the condition is for), and will do some escaping to prevent formatting issues, but shortened Twitter URLs and embedded images for example, are still shown as (short) t.co links instead of their intrinsic content or location. Improvements or suggestions are always welcomed.

Happy tooting!

Security Updates Exchange 2013-2019 (Oct2022)

Posted on October 11, 2022 by Michel de Rooij

The Exchange product group released October updates for Exchange Server 2013, 2016 and 2019. Note that these Security Updates do NOT address the vulnerabilities CVE-2022-41040 and CVE-2022-41082 that have been reported on since end of September. For now, mitigate those by follow the instructions mentioned an earlier post here.

The vulnerabilities addressed in these Security Updates are mostly the same as the ones addressed by the Security Updates of August, with the exception of CVE-2022-34692. Also, the CVSS rating of CVE-2022-30134 has been adjusted:

Vulnerability	Category	Severity	Rating
CVE-2022-21979	Information Disclosure	Important	CVSS:3.1 4.8 / 4.2
CVE-2022-21980	Elevation of Privilege	Critical	CVSS:3.1 8.0 / 7.0
CVE-2022-24477	Elevation of Privilege	Critical	CVSS:3.1 8.0 / 7.0
CVE-2022-24516	Elevation of Privilege	Critical	CVSS:3.1 8.0 / 7.0
CVE-2022-30134	Elevation of Privilege	Important	CVSS:3.1 6.5 / 5.7 (was CVSS:3.1 7.6 / 6.6)

The following Security Updates address these vulnerability for the Exchange builds mentioned:

Exchange	Download	Build	KB	Supersedes
Exchange 2019 CU12	Download	15.2.1118.15	KB5019077	KB5015322
Exchange 2019 CU11	Download	15.2.986.30	KB5019077	KB5015322
Exchange 2016 CU23	Download	15.1.2507.13	KB5019077	KB5015322
Exchange 2016 CU22	Download	15.1.2375.32	KB5019077	KB5015322
Exchange 2013 CU23	Download	15.0.1497.42	KB5019076	KB5015321

Be advised that these security updates are Cumulative Update level specific. You cannot apply the update for Exchange 2019 CU12 to Exchange 2019 CU11. Also, the security update download has the same name for different Cumulative Updates, and I would suggest tagging the file name with the CU level, e.g. Exchange2019-CU12-KBXXXXXX-x64-en.msp.

Exchange 0-days: CVE-2022-41040 & CVE-2022-41082

Posted on October 3, 2022 by Michel de Rooij

Update (Oct10, 2022): Updated URL Rewrite Rule (again).

End of last week, the Exchange world was made aware of a 0-day vulnerability and exploit through the following tweet by security researcher Kevin Beaumont. The tweet referenced a write-up by GTSC Cyber Security, which published their discovery on a what looked like a variation on ProxyShell, allowing for Remote code execution. The vulnerabilities have been registered by the Common Vulnerabilities and Exposures program as CVE-2022-41040 (ZDI-CAN-18333 at Zero Day Initiative) and CVE-2022-41082 (ZDI-CAN-18802).

The 0-day impacts current versions of Exchange Server 2019, Exchange Server 2016 as well as Exchange Server 2013 when published externally. If you have Exchange Hybrid deployed only for recipient management or mail-flow (i.e. no inbound traffic for https/443), you should be OK. Similar to ProxyShell, the vulnerability consists of sending manufactured requests to Exchange server, e.g.

Read the full of this article on ENow here.

Update (Oct10): The (original) filter to mitigate the situation, as specified originally by the GTSC as well as various websites, is too specific. The filter can easily be circumvented by – but effectively identical – variations on the manufactured request. The latest rule to filter requests is:

(?=.*autodiscover)(?=.*powershell)

Update any existing mitigation IIS URL Rewrite Rules with this Regular Expressions filter for {UrlDecode:{REQUEST_URI}} blocking (Abort Request) any matching request. When using EEMS, this rule will also be deployed in the most recent update (1.0.9). Microsoft rather silently updated the filter in their published EEMS rules during the weekend.

Microsoft added to their advisory, recommending organizations to disable Remote PowerShell for non-administrators roles (instructions here). For those wanting to hunt for indicators of compromise, check the end of the Security blog.

Vendors are also offering solutions to filter these requests using their network devices:

At the time of writing, Microsoft has not publish a security fix yet.

MEC 2022 Sessions Downloading

Posted on September 19, 2022 by Michel de Rooij

Update 9/29/2022: By popular request, I modified the Get-EventSession script so it is now able to also download MEC sessions (-Event MEC). See below for details.

A quick post for those that are looking for a simple way to download the Microsoft Exchange Community (MEC) Technical Airlift 2022 sessions for offline viewing, here’s a simple way to accomplish this:

Get youtube-dl.exe here. Youtube-dl is a tool to download videos or playlists from Youtube.
Get aria2c.exe here. Aria2c can be used to download media using multiple streams, reducing time it takes to download video content.
Put the executables from both downloads in the same folder, and, using a a (PowerShell) command prompt, run the following:

.\youtube-dl.exe -o "C:\MEC2022\%(playlist_index)s-%(title)s.mp4" --external-downloader aria2c --external-downloader-args "-x 16 -k 1M" https://www.youtube.com/playlist?list=PLxdTT6-7g--2POisC5XcDQxUXHhWsoZc9

“C:\MEC2022” is the folder where the downloaded files will be stored. Change when needed. For file naming, variables are used with define the name of the downloaded files using a prefix of the sequence number (from the playlist) together with the title of the video (session).
–external-downloader tells youtube-dl to use specified download utility (aria2c) instead of its own engine. The external-downloader-args parameters define concurrency and chunk size.
The last part is the URL for the MEC 2022 playlist.

9/29/2022: Alternatively, you can now use Get-EventSession (version 3.7 and up) to download MEC sessions. The script will parse the information shared through the playlist, but some usual attributes are missing, but there also some new attributes, such as likes and views. To use the script to download MEC session videos:

Get-EventSession> .\Get-EventSession.ps1 -Event MEC -DownloadFolder c:\MEC20222 -Format 22 -Speaker 'Michel de Rooij'

Few notes:

As there are no session codes in the YouTube metadata, session code is set to equal the playlist index.
Speaker names will be extracted from the description when present.
The session timestamp will be the upload date of the video.
Likes, Views and Duration are YouTube specific properties returned.

Using views and likes, you can do cool things such as get a scoreboard of the Top 10 most viewed videos from MEC playlist:

.\Get-EventSession.ps1 -Event MEC -InfoOnly | Sort Views -desc | Select -First 10 Title,SpeakerNames, Views, Likes

Note: If you do not specify format, YouTube videos will be downloaded in ‘best’ possible quality, which will be .webm by default. You can prevent this, and download 1080p movies, by specifying -Format 22.