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

Update (Oct5, 2022): Updated URL Rewrite Rule to filter on URL decoded URI.

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 (Oct3): The (original) filter to mitigate the situation, specified 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. A more broad rule to filter requests is:

.*autodiscover\.json.*Powershell.*  

Update any existing mitigation IIS URL Rewrite Rules with this Regular Expressions filter for {UrlDecode:{REQUEST_URI}} blocking any matching request. If you depend on the EEMS rules, I recommend manually configuring this rule as EEMS might overwrite its own managed URL Rewrite rules with the outdated rule.

Microsoft updated their advisory, and is now also 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.

Update (Oct4): Microsoft updated the rules pushed via EEMS, which now also reflects the more broader filter. Vendors are also offering solutions to filter these requests using their network components, e.g.

Update (Oct5): The filter works pre-URL decoding, meaning one can simply replace any character in the URI with its %<code> counterpart, rendering the filter ineffective. To counter this, explicitly state you want to filter on the URL Decoded string of the request’s URI – see instructions above for updated guidance.

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

MEC: Bringing your Exchange Scripts into the Modern Age

Yesterday, I had the pleasure of presenting at the Microsoft Exchange Conference Community Technical Airlift 2022. I talked about the challenges that organizations are facing that use Exchange scripts in their work processes or run them scheduled unattended.

Some of the challenges I mentioned, apart from the upcoming demise of Basic Authentication, and resources to methodically assess and make the necessary changes, are:

  • Get your code more secure leveraging Certificate Based Authentication, especially for scheduled tasks.
  • Get current with the most recent version of the Exchange Online Management Module for PowerShell.
  • The same exercise with regards to AzureAD when using MSOnline or AzureAD modules, and the inevitable move to the PowerShell Graph SDK.

In the end I also quickly demonstrated how much easier and secure things can be when utilizing Azure Automation, which might especially appeal to organizations that want to totally get rid of any infrastructure for running jobs.

You can watch the presentation below. All sessions are you published on YouTube, and its playlist can be accessed at aka.ms/MEC2022.

The presentation as well as the deck and script used in the live demonstration can be retrieved from GitHub. The Analyse-ExoScript used in the demo can be found on GitHub as well, or look at the accompanying blog I wrote a while ago here.

Note that during MEC, it was announced that the next GA release of the Exchange Online Management module will be version 3. This jump is doneto prevent any confusion with earlier GA and preview releases. It was said the next GA release might be as early as next week, which should be good news for organizations who’s policy it is to not run Preview software in production environments.

If you have any questions, ask them in the comments or send me a message via the contact form.

MEC Airlift 2022 #WeAreMEC

It seems ages ago – 8½ years to be exact – that the most recent Microsoft Exchange Conference took place in Austin in 2014. Much has happened since then, Exchange Online became a thing and there seemed to be no need for Microsoft to host an Exchange themed conference any longer. All this while events around products such as SharePoint did not slow down a single bit.

Then the pandemic happened, and we went to zero in-person conferences. It did not take long online/virtual/digital conferences took off. But alas, no Exchange conference. Until 2022 arrived, and Microsoft announced continued commitment to Exchange on-premises. Now, early in the FY22/23, a free 2-day online event will take place on September 13th & 14th, the Microsoft Exchange Conference Community Technical Airlift 2022. Target audience are IT professionals working with Exchange Online/On-Premises as well people developing solutions that integrate with Exchange. While nothing comes close to the experience and value of an in-person event, MEC 2022 will take place online. I am guessing that if this event is a success, and there is enough content to talk about as well as interest, that might switch to becoming at least a hybrid event, with a mix of an in-person and online audience, similar to Microsoft Ignite this year.

The agenda for MEC 2022 looks very promising, with sessions from both the Exchange product group as well as some very smart people from the Exchange community. Not totally surprising, there are sessions on the demise of Basic Authentication and how to deal with that, hosted by Greg Taylor. Also have a look at Scott Schnoll’s famous Exchange Tips & Tricks, or Jeff Mealiffe talking about connectivity. The event kicks off with a welcome keynote with Perry Clarke and Rajesh Jha. You can still submit questions for this “Geek Out with Perry!” here.

Yours truly will also present at MEC, presenting “Bringing your Exchange Scripts into the Modern Age” on September 14th, 9:00am PDT. Note that MEC sessions will be recorded, and will be made available for on-demand viewing after the event, which is great in case you cannot attend sessions as they happen. You can still register for MEC at https://aka.ms/MECAirlift.

If I do not “see” you at MEC, there is also an opportunity to have an in-person chat next week in Atlanta, where I will be attending – not presenting as I missed the submit deadline – The Experts Conference, or just TEC. It seems you can still register, but Anyway, it is good to see Exchange themed events pick-up and confereces in general returning to a certain level of pre-pandemic numbers, as there is enough to talk about, discuss and learn from others.

The Last Exchange Server

In the announcement of the most recent set of Cumulative Updates for Exchange Server 2019 and 2016, Microsoft introduced some changes – features if you will – as well, which were received with enthusiasm. An overview of these Cumulative Updates and the features introduced was given in an earlier article. In this article however, I would like to zoom in on one of those features, which also happens to be a popular topic among customers running Exchange Hybrid deployments, “The Last Exchange Server”.

Up to Exchange 2019 CU12 (2022 H1), customers that migrated to Exchange Online were still required to leave Exchange-related components running on-premises. Even today, with all the information published around this topic, I am surprised this still surprised customers. This Exchange server running on-premises is to be used for managing recipients which have their source of authority in Active Directory, leveraging Active Directory Connect to propagate objects to Azure Active Directory and thus Exchange Online. Also, when there is a need to relay messages from applications or multi-functional devices, customers often need to have an Exchange server on-premises to accept these messages, as Exchange is the only supported mail relay product for hybrid deployments.

Click here to read the full article on ENow Solutions blog.

Exchange Updates (and more) – H1 2022

20220423: Added TLS 1.3 note.

The Exchange Team released the quarterly half-yearly Cumulative Updates for Exchange Server 2019 and Exchange 2016. You read that right, half-yearly updates are replacing the cadence of quarterly update servicing model for Exchange Server. Effectively, this will be Exchange 2019 only, as Exchange 2016 will be out of mainstream support in H2 of 2022, and will therefor only receive Security Updates after this round. Note that this change also alters the effective ‘current’ state (n-1 or later) of your Exchange Server environment from half year to one year.

And that’s not the only good news that comes with these sets of updates. In short:

  • If you run Exchange 2019 in Hybrid only for the purpose of managing recipients, you can now use Exchange 2019 CU12’s Exchange Management Tools to accomplish this; no more need to have an Exchange server running just for this. More details here.
  • Exchange 2019 CU12 will reintroduce the Hybrid Key option. Its Hybrid Configuration Wizard supports this licensing method.
  • Exchange 2019 CU12 support managing the Hybrid Agent with MFA-enabled accounts.
  • Exchange 2019 CU12 adds support for Windows Server 2022, both for its underlying operating system, as well as deployment in environments running Windows Server 2022 Domain Controllers.
  • Note that while Windows Server 2022 supports TLS 1.3, Exchange 2019 CU12 on WS2022 does not yet support it. Adding support is scheduled for somewhere next year.
  • The supportability matrix has been updated for the supported Windows Server 2022 scenarios.
  • Exchange Server is now also part of Microsoft’s Bounty Program, which is an indication of continued focus for customers still running Exchange Servers on-premises.

Links to the updates as well as a description of changes and fixes are described 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.

VersionBuildKBDownloadUMLPSchemaAD
Exchange 2019 CU1215.2.1118.7KB5011156Download NY
Exchange 2016 CU2315.1.2507.6KB5011155DownloadUMLPNY

Apart from DST changes and the fixes mentioned below, these Cumulative Updates also contain a change which will not allow using UNC paths with several cmdlets. More information about this change and cmdlets affected can be found here: KB5014278.

Exchange 2019 CU12 fixes:

  • 5012757 “Migration user… can’t be found” error when using Start-MigrationUser after batch migration fails
  • 5012758 Start-MailboxAssistant is not available in Exchange Server 2019
  • 5012760 You can’t access OWA or ECP after installing the July 2021 security update
  • 5012761 External attendees see “Send the Response Now” although no response was requested in Exchange Server
  • 5012762 PST creation is unexpectedly triggered again during multiple mailbox export
  • 5012765 Email stuck in queue starting from “2022/1/1 00:01:00 UTC+0” on all Exchange on-premises servers
  • 5012766 Transport Services fail repeatedly because of * Accepted Domain
  • 5012768 Start-MigrationUser and Stop-MigrationUser are unavailable for on-premises Exchange Server 2019 and 2016
  • 5012769 Invalid New Auth Certificate for servers that are not on UTC time zone
  • 5012770 No response from public folder for users migrating to Microsoft Exchange 2019
  • 5012772 Items are skipped at the start of a new search page request
  • 5012773 OWAMailboxPolicy is bypassed and high resolution profile images can be uploaded
  • 5012774 Can’t change default path for Trace log data in Exchange Server 2019 and 2016
  • 5012775 No additional global catalog column in the address book service logs
  • 5012776 Exchange Server 2019 help link in OWA redirects users to online help for Exchange Server 2016
  • 5012777 Can’t find forwarded messages that contain attachments in Exchange Server 2019
  • 5012778 Exchange Server stops responding when processing PDF files with set transport rule
  • 5012779 Invalid new auth certificate for servers that are not on UTC time zone
  • 5012780 Disable-Mailbox does not remove LegacyExchangeDN attribute from on-premises Exchange 2019
  • 5012781 Exchange Server 2019 and 2016 DLP doesn’t detect Chinese resident ID card numbers
  • 5012782 MS ExchangeDiagnostic Service causes errors during service startup and initialization in Microsoft Exchange 2019
  • 5012783 Can’t restore data of a mailbox when LegacyDN is empty in the database
  • 5012784 Exchange 2016 CU21 and Exchange 2019 CU10 cannot save “Custom Attributes” changes in EAC
  • 5012785 Read Only Domain Controllers (RODCs) in other domains do not get desired permissions
  • 5012786 Forwarded meeting appointments are blocked or considered spam
  • 5012787 Download domains created per CVE-2021-1730 don’t support ADFS authentication in OWA
  • 5012789 Can’t use Copy Search Results after eDiscovery & Hold search
  • 5012790 OWA doesn’t remove the “loading” image when a message is opened in Chrome and Edge browsers
  • 5012791 MailboxAuditLog doesn’t work in localized (non-English) environments

Exchange 2016 CU23 fixes:

  • 5012757 “Migration user… can’t be found” error when using Start-MigrationUser after batch migration fails
  • 5012760 You can’t access OWA or ECP after installing the July 2021 security update
  • 5012761 External attendees see “Send the Response Now” although no response was requested in Exchange Server
  • 5012765 Email stuck in queue starting from “2022/1/1 00:01:00 UTC+0” on all Exchange on-premises servers
  • 5012768 Start-MigrationUser and Stop-MigrationUser are unavailable for on-premises Exchange Server 2019 and 2016
  • 5012769 Invalid New Auth Certificate for servers that are not on UTC time zone
  • 5012774 Can’t change default path for Trace log data in Exchange Server 2019 and 2016
  • 5012779 Invalid new auth certificate for servers that are not on UTC time zone
  • 5012780 Disable-Mailbox does not remove LegacyExchangeDN attribute from on-premises Exchange 2019
  • 5012781 Exchange Server 2019 and 2016 DLP doesn’t detect Chinese resident ID card numbers
  • 5012782 MS ExchangeDiagnostic Service causes errors during service startup and initialization in Microsoft Exchange 2019
  • 5012783 Can’t restore data of a mailbox when LegacyDN is empty in the database
  • 5012784 Exchange 2016 CU21 and Exchange 2019 CU10 cannot save “Custom Attributes” changes in EAC
  • 5012786 Forwarded meeting appointments are blocked or considered spam
  • 5012787 Download domains created per CVE-2021-1730 don’t support ADFS authentication in OWA
  • 5012789 Can’t use Copy Search Results after eDiscovery & Hold search
  • 5012791 MailboxAuditLog doesn’t work in localized (non-English) environments
  • 5012829 Group metrics generation fails in multidomain environment

Notes:

  • If these 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).
  • 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.

Exchange Updates – September 2021

The Exchange Team released the quarterly Cumulative Updates for Exchange Server 2019 as well as Exchange 2016.

Be advised that these CUs will introduce something which is called the Exchange Emergency Mitigation Service. This service is designed to distribute and implement mitigations addressing potential threats. For this, the URL Rewrite Module needs to be installed on the Exchange server. When you have Exchange running on Windows Server 2012 R2, you will also need an update for the Universal C Runtime (KB2999226). Periodically, the EEM service will reach out to the Office Config Service (OCS) through endpoint https://officeclient.microsoft.com, and update its set of configured mitigations. More on EEM and managing its configuration here.

Links to the updates as well as a description of changes and fixes are described 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.

VersionBuildKBDownloadUMLPSchemaAD
Exchange 2019 CU1115.2.986.5KB5005334Download NY
Exchange 2016 CU2215.1.2375.7KB5005333DownloadUMLPNY

Exchange 2019 CU11 fixes:

  • 5006980 Bad signature error using PerfView in Exchange Server 2019 and 2016 (KB5006980)
  • 5006982 On-premises Exchange queues back up because of incorrect default value (KB5006982)
  • 5006983 Exchange Server 2019 and 2016 certificates created during setup use SHA-1 hash (KB5006983)
  • 5006984 PrepareAD fails if Computers container or RODCs are renamed or moved in Exchange Server 2019 and 2016 (KB5006984)
  • 5006986 Opening an Outlook message from the desktop removes line spacing (KB5006986)
  • 5006988 Export of .pst file is unexpectedly triggered again in Exchange Server 2019 and 2016 (KB5006988)
  • 5006989 Accepted domains with wildcards for subdomains are not honored when Edge server maps AddressSpaces (KB5006989)
  • 5006990 Exchange CU installation fails after you configure fallback to use default character set (5006990)
  • 5006991 Mail quota warning messages no longer sent daily in Exchange Server 2019 (KB5006991)
  • 5006992 No room lists found when trying to add a room in OWA in Exchange Server 2019 or 2016 (KB5006992)
  • 5006993 Can’t log on to OWA in Chrome if SSL is offloaded in Exchange Server 2019 and 2016 (KB5006993)
  • 5006994 BCC values not retained in Sent Items in a shared mailbox in Exchange Server 2019 and 2016 (5006994)
  • 5006995 Korean email messages display some recipients incorrectly in Exchange Server 2019 and 2016 (KB5006995)
  • 5006996 Export-AutoDiscoverConfig exposes admin password and does not work against domain controllers that require signing (KB5006997)
  • 5006997 Korean messages in OWA display “From” as “Start date” after you filter the list in Exchange Server 2019 and 2016
  • 5006999 “401” error and Outlook repeatedly prompts for credentials in Exchange Server 2019 (KB5006999)
  • 5007042 Error window appears when you view features in OWA Virtual Directory (KB5007042)
  • 5007043 Exchange Server SU updates Add/Remove Programs incorrectly (KB5007043)
  • 5007044 Start-MailboxAssistant not available in EMS in Exchange Server 2019 (KB5007044)

Exchange 2016 CU22 fixes:

  • 5006980 Bad signature error using PerfView in Exchange Server 2019 and 2016 (KB5006980)
  • 5006982 On-premises Exchange queues back up because of incorrect default value (KB5006982)
  • 5006983 Exchange Server 2019 and 2016 certificates created during setup use SHA-1 hash (KB5006983)
  • 5006984 PrepareAD fails if Computers container or RODCs are renamed or moved in Exchange Server 2019 and 2016 (KB5006984)
  • 5006986 Opening an Outlook message from the desktop removes line spacing (KB5006986)
  • 5006988 Export of .pst file is unexpectedly triggered again in Exchange Server 2019 and 2016 (KB5006988)
  • 5006989 Accepted domains with wildcards for subdomains are not honored when Edge server maps AddressSpaces (KB5006989)
  • 5006992 No room lists found when trying to add a room in OWA in Exchange Server 2019 or 2016 (KB5006992)
  • 5006993 Can’t log on to OWA in Chrome if SSL is offloaded in Exchange Server 2019 and 2016 (KB5006993)
  • 5006994 BCC values not retained in Sent Items in a shared mailbox in Exchange Server 2019 and 2016 (5006994)
  • 5006995 Korean email messages display some recipients incorrectly in Exchange Server 2019 and 2016 (KB5006995)
  • 5006996 Export-AutoDiscoverConfig exposes admin password and does not work against domain controllers that require signing (KB5006997)
  • 5006997 Korean messages in OWA display “From” as “Start date” after you filter the list in Exchange Server 2019 and 2016
  • 5007042 Error window appears when you view features in OWA Virtual Directory (KB5007042)
  • 5007043 Exchange Server SU updates Add/Remove Programs incorrectly (KB5007043)

Notes:

  • If these Cumulative Updates contain schema changes compared to the Cumulative Update you 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).
  • 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.

Exchange Updates – December 2020

The Exchange Team released the quarterly Cumulative Updates for Exchange Server 2019 as well as Exchange 2016. Be advised that Exchange 2016 will receive its final CU in March, 2021.

Links to the updates as well as a description of changes and fixes are described below.

VersionBuildKBDownloadUMLPSchemaPrepareAD
Exchange 2019 CU815.2.792.3KB4588885VLSC NY
Exchange 2016 CU1915.1.2176.2KB4588884DownloadUMLPNY

Exchange 2019 CU8 fixes:

  • 4588297 Attachments can’t be downloaded or previewed from Outlook Web App
  • 4583531 Design change about inline images will be forced to download but not open in a new tab of OWA in Exchange Server 2019
  • 4583532 ELC MRM archiving fails due to DomainName in AuthServer in Exchange Server 2019
  • 4583533 Exchange Server 2019 installation fails with error “The user has insufficient access rights” 
  • 4583534 Event ID 65535 System.Runtime.Serialization errors in Application log in Exchange Server 2019
  • 4583535 New-Moverequest, Resume-Moverequest, and Remove-Moverequest not logged in Audit logs in Exchange Server 2019
  • 4583536 Set-MailboxFolderPermission is included in Mail Recipient Creation in Exchange Server 2019
  • 4583537 Update Korean word breaker in Exchange Server 2019
  • 4583538 Microsoft Teams REST calls exceed the default value of maxQueryStringLength in Exchange Server 2019
  • 4583539 Non-breaking space is visible in message body in Outlook in Exchange Server 2019
  • 4583542 Server assisted search in Outlook doesn’t return more than 175 items in Exchange Server 2019
  • 4583544 Lots of LDAP requests for FE MAPI w3wp lead to DDoS on DCs in Exchange Server 2019
  • 4583545 Make DomainName in Authserver a multivalued parameter in Exchange Server 2019
  • 4593465 Description of the security update for Microsoft Exchange Server 2019 and 2016: December 8, 2020

Exchange 2016 CU19 fixes:

  • 4588297 Attachments can’t be downloaded or previewed from Outlook Web App
  • 4583531 Design change about inline images will be forced to download but not open in a new tab of OWA in Exchange Server 2016
  • 4583532 ELC MRM archiving fails due to DomainName in AuthServer in Exchange Server 2016
  • 4583533 Exchange Server 2016 installation fails with error “The user has insufficient access rights” 
  • 4583534 Event ID 65535 System.Runtime.Serialization errors in Application log in Exchange Server 2016
  • 4583535 New-Moverequest, Resume-Moverequest, and Remove-Moverequest not logged in Audit logs in Exchange Server 2016
  • 4583536 Set-MailboxFolderPermission is included in Mail Recipient Creation in Exchange Server 2016
  • 4583537 Update Korean word breaker in Exchange Server 2016
  • 4583538 Microsoft Teams REST calls exceed the default value of maxQueryStringLength in Exchange Server 2016
  • 4583539 Non-breaking space is visible in message body in Outlook in Exchange Server 2016
  • 4583545 Make DomainName in Authserver a multivalued parameter in Exchange Server 2016
  • 4593465 Description of the security update for Microsoft Exchange Server 2019 and 2016: December 8, 2020

Notes:

  • These Cumulative Updates contain schema changes compared to the previous Cumulative Update. This requires you to run /PrepareSchema. Also, Active Directory changes require you to run PrepareAD (which also can perform the schema update, depending permissions). Consult the Exchange schema versions page for object version numbers.
  • 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), you are allowed to trail at most one version (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; 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 of installation shouldn’t matter with the “every server is an island” concept, yet recommended is to upgrade 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.

Security Updates Exchange 2010-2019 (Dec2020)

A quick blog on security updates for Exchange Server 2013, 2016 and 2019 released December 8th. These fixes address the following vulnerability:

Exchange 2016 / 2019

  • CVE-2020-17117: Microsoft Exchange Remote Code Execution Vulnerability
  • CVE-2020-17132: Microsoft Exchange Remote Code Execution Vulnerability
  • CVE-2020-17141: Microsoft Exchange Remote Code Execution Vulnerability
  • CVE-2020-17142: Microsoft Exchange Remote Code Execution Vulnerability
  • CVE-2020-17143: Microsoft Exchange Information Disclosure Vulnerability

Exchange 2013

  • CVE-2020-17117: Microsoft Exchange Remote Code Execution Vulnerability
  • CVE-2020-17132: Microsoft Exchange Remote Code Execution Vulnerability
  • CVE-2020-17142: Microsoft Exchange Remote Code Execution Vulnerability
  • CVE-2020-17143: Microsoft Exchange Information Disclosure Vulnerability

Exchange 2010

  • CVE-2020-17144: Microsoft Exchange Remote Code Execution Vulnerability

The exploits can be fixed by single security update, which you can find in the table below per current Exchange version.

ExchangeDownloadBuildKBSupersedes
Exchange 2019 CU7Download15.2.721.6KB4593465KB4588741
Exchange 2019 CU6Download15.2.659.11KB4593465KB4588741
Exchange 2016 CU18Download15.1.2106.6KB4593465KB4588741
Exchange 2016 CU17Download15.1.2044.12KB4593465KB4588741
Exchange 2013 CU23Download15.0.1497.10KB4593466
Exchange 2010 SP3 RU31 Download14.3.509.0KB4593467

Be advised that these security updates are Cumulative Update level specific. You cannot apply the update for Exchange 2016 CU17 to Exchange 2016 CU16. 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-CU6-KB4588741-x64-en.msp.

Also, run the Security Update from an elevated command prompt, to prevent issues during installation. And on a final note, as with any patch or update, I’d recommend to apply this in a acceptance environment first, prior to implementing it in production.

Security Updates Exchange 2013-2019 (Nov2020)

A quick blog on security updates for Exchange Server 2013, 2016 and 2019 released November 10th. These fixes address the following vulnerability:

  • CVE-2020-17085: Microsoft Exchange Server Denial of Service Vulnerability
  • CVE-2020-17084: Microsoft Exchange Server Remote Code Execution Vulnerability
  • CVE-2020-17083: Microsoft Exchange Server Remote Code Execution Vulnerability

The exploits can be fixed by single security update, which you can find in the table below per current Exchange version.

ExchangeDownloadBuildKBSupersedes
Exchange 2019 CU7Download15.2.721.4KB4588741KB4581424
Exchange 2019 CU6Download15.2.659.8KB4588741KB4581424
Exchange 2016 CU18Download15.1.2106.4KB4588741KB4581424
Exchange 2016 CU17Download15.1.2044.8KB4588741KB4581424
Exchange 2013 CU23Download15.0.1497.8KB4588741KB4581424

Be advised that these security updates are Cumulative Update level specific. You cannot apply the update for Exchange 2016 CU17 to Exchange 2016 CU16. 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-CU6-KB4588741-x64-en.msp.

Also, run the Security Update from an elevated command prompt, to prevent issues during installation. And on a final note, as with any patch or update, I’d recommend to apply this in a acceptance environment first, prior to implementing it in production.

Security Updates Exchange 2013-2019 (Oct2020)

A quick blog on security updates for Exchange Server 2013, 2016 and 2019 released October 13th. These fixes address the following vulnerability:

  • CVE-2020-16969: Microsoft Exchange Information Disclosure Vulnerability
    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.

The exploits can be fixed by single security update, which you can find in the table below per current Exchange version.

ExchangeDownloadBuildKBSupersedes
Exchange 2019 CU7Download15.2.721.3KB4581424KB4577352
Exchange 2019 CU6Download15.2.659.7KB4581424KB4577352
Exchange 2016 CU18Download15.1.2106.3KB4581424KB4577352
Exchange 2016 CU17Download15.1.2044.7KB4581424KB4577352
Exchange 2013 CU23Download15.0.1497.7KB4581424KB4536988

Be advised that these security updates are Cumulative Update level specific. You cannot apply the update for Exchange 2016 CU17 to Exchange 2016 CU16. 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. Exchange2016-CU17-KB4581424-x64-en.msp.

Also, run the Security Update from an elevated command prompt, to prevent issues during installation. And on a final note, as with any patch or update, I’d recommend to apply this in a acceptance environment first, prior to implementing it in production.