windows kerberos authentication breaks due to security updates

Once all audit events have been resolved and no longer appear, move your domains to Enforcement modeby updating the KrbtgtFullPacSignature registry value as described in Registry Key settingssection. After installing updates released May 10, 2022 on your domain controllers, you might see authentication failures on the server or client for services such as Network Policy Server (NPS), Routing and Remote access Service (RRAS), Radius, Extensible Authentication Protocol (EAP), and Protected Extensible Authentication Protocol (PEAP). Updates will be released in phases: the initial phase for updates released on or after November 8, 2022 and the Enforcement phase for updates released on or after April 11, 2023. For more information about Kerberos Encryption types, see Decrypting the Selection of Supported Kerberos Encryption Types. Domains that have third-party domain controllers might see errors in Enforcement mode. The Windows updates released on or after April 11, 2023 will do the following: Remove the ability to disable PAC signature addition by setting the KrbtgtFullPacSignaturesubkey to a value of 0. To learn more about these vulnerabilities, see CVE-2022-37966. If you used any workaround or mitigations for this issue, they are no longer needed, and we recommend you remove them. Explanation: This is warning you that RC4 is disabled on at least some DCs. I don't know if the update was broken or something wrong with my systems. There was a change made to how the Kerberos Key Distribution Center (KDC) Service determines what encryption types are supported and what should be chosen when a user requests a TGT or Service Ticket. Find out more about the Microsoft MVP Award Program. To deploy the Windows updates that are dated November 8, 2022 or later Windows updates, follow these steps: UPDATEyour Windows domain controllers with an update released on or after November 8, 2022. It is a network service that supplies tickets to clients for use in authenticating to services. Microsoft confirmed that Kerberos delegation scenarios where . Note: This issue should not affect other remote access solutions such as VPN (sometimes called Remote Access Server or RAS) and Always On VPN (AOVPN). If you useMonthly Rollup updates, you will need to install both the standalone updates listed above to resolve this issue, and install the Monthly Rollups released November 8, 2022, to receive the quality updates for November 2022. So now that you have the background as to what has changed, we need to determine a few things. The beta and preview chanels don't actually seem to preview anything resembling releases, instead they're A/B testing which is useless to anyone outside of Microsoft. Server: Windows Server 2008 SP2 or later, including the latest release, Windows Server 2022. There is also a reference in the article to a PowerShell script to identify affected machines. Audit mode will be removed in October 2023, as outlined in theTiming of updates to address Kerberos vulnerabilityCVE-2022-37967 section. If a service ticket has invalid PAC signatureor is missing PAC signatures, validation will fail and an error event will be logged. You might have authentication failures on servers relating to Kerberos Tickets acquired via S4u2self. This behavior has changed with the updates released on or afterNovember 8, 2022and will now strictly follow what is set in the registry keys, msds-SupportedEncryptionTypes and DefaultDomainSupportedEncTypes. After the latest updates, Windows system administrators reported various policy failures. This known issue was resolved in out-of-band updates released November 17, 2022 and November 18, 2022 for installation onalldomain controllersin your environment. RC4 should be disabled unless you are running systems that cannot use higher encryption ciphers. For more information about how to do this, see theNew-KrbtgtKeys.ps1 topic on the GitHub website. Monthly Rollup updates are cumulative and include security and all quality updates. For more information, see what you shoulddo first to help prepare the environment and prevent Kerberos authentication issues. The update, released Sunday, should be applied to Windows Server 2008, 2012, 2016 and 2019 installations where the server is being used as a domain controller. The requested etypes were 18 17 23 24 -135. Experienced issues include authentication issues when using S4U scenarios, cross-realm referrals failures on Windows and non-Windows devices for Kerberos referral tickets, and certain non-compliant Kerberos tickets being rejected, depending on the value of the PerformTicketSignature setting. To help secure your environment, install theWindows update that is dated November 8, 2022 or a later Windows update to all devices, including domain controllers. I'm hopeful this will solve our issues. Moves the update to Enforcement mode (Default) (KrbtgtFullPacSignature = 3)which can be overridden by an Administrator with an explicit Audit setting. The process I setting up the permissions is: Create a user mssql-startup in the OU of my domain with Active Directory Users and Computers. The November 8, 2022 Windows updates address security bypass and elevation of privilege vulnerabilities with Privilege Attribute Certificate (PAC) signatures. Online discussions suggest that a number of . <p>Hi All, </p> <p>We are experiencing the event id 40960 from half of our Windows 10 workstations - ( These workstations are spread across different sites ) . If any of these have started around the same time as the November security update being installed, then we already know that the KDC is having issues issuing TGT or Service tickets. After installing updates released on November 8, 2022 or later, on Windows servers with the role of a domain controller, you may experience problems with Kerberos authentication. The Kerberos service that implements the authentication and ticket granting services specified in the Kerberos protocol. NoteIf you need to change the KrbtgtFullPacSignatureregistry value, manuallyadd and then configure the registry key to override the default value. Installation of updates released on or after November 8, 2022on clients or non-Domain Controller role servers should not affect Kerberos authentication in your environment. For more information, see[SCHNEIER]section 17.1. To fully mitigate the security issue for all devices, you must move to Audit mode (described in Step 2) followed by Enforced mode (described in Step 4) as soon as possible on all Windows domain controllers. Microsoft is working on a fix for this known issue and estimates that a solution will be available in the coming weeks. Can I expect msft to issue a revision to the Nov update itself at some point? The Ticket-granting Ticket (TGT) is obtained after the initial authentication in the Authentication Service (AS) exchange; thereafter, users do not need to present their credentials, but can use the TGT to obtain subsequent tickets. To find Supported Encryption Types you can manually set, please refer to Supported Encryption Types Bit Flags. Windows Server 2012: KB5021652 reg add "HKLM\\SYSTEM\\CurrentControlSet\\services\\kdc" /v KrbtgtFullPacSignature /t REG\_DWORD /d 0 /f Sharing best practices for building any app with .NET. 16 DarkEmblem5736 1 mo. Microsoft last week released an out-of-band update for Windows to address authentication issues related to a recently patched Kerberos vulnerability. Client : /. Should I not patch IIS, RDS, and Files Servers? but that's not a real solution for several reasons, not least of which are privacy and regulatory compliance concerns. Next StepsInstall updates, if they are available for your version of Windows and you have the applicable ESU license. The service runs on computers selected by the administrator of the realm or domain; it is not present on every machine on the network. MOVE your domain controllers to Audit mode byusing the Registry Key settingsection. Errors logged in system event logs on impacted systems will be tagged with a "the missing key has an ID of 1" keyphrase. AES can be used to protect electronic data. To mitigate the issues, you will need to investigate your domain further to find Windows domain controllers that are not up to date. If the account does have msds-SupportedEncryptionTypes set, this setting is honored and might expose a failure to have configured a common Kerberos Encryption type masked by the previous behavior of automatically adding RC4 or AES, which is no longer the behavior after installation of updates released on or after November 8, 2022. First, we need to determine if your environment was configured for Kerberos FAST, Compound Identity, Windows Claims or Resource SID Compression. BleepingComputer readers also reported three days ago that the November updates break Kerberos "in situations where you have set the 'This account supports Kerberos AES 256 bit encryption' or 'This account supports Kerberos AES 128 bit encryption' Account Options set (i.e., msDS-SupportedEncryptionTypes attribute) on user accounts in AD." Windows Server 2008 SP2: KB5021657, oh well even after we patched with the November 17, 2022, we see Kerberos authentication issues. Authentication protocols enable authentication of users, computers, and services, making it possible for authorized services and users to access resources in a secure manner. The solution is to uninstall the update from your DCs until Microsoft fixes the patch. Configurations where FAST/Windows Claims/Compound Identity/Disabled Resource SID Compression were implemented had no impact on the KDCs decision for determining Kerberos Encryption Type. To learn more about thisvulnerabilities, seeCVE-2022-37967. If the server name is not fully qualified, and the target domain (ADATUM.COM) is different from the client domain (CONTOSO.COM), check if there are identically named server accounts in these two domains, or use the fully-qualified name to identify the server.Possible problem: Account hasn't had its password reset (twice) since AES was introduced to the environment or some encryption type mismatch. RC4-HMAC (RC4) is a variable key-length symmetric encryption algorithm. If the Windows Kerberos Client on workstations/Member Servers and KDCs are configured to ONLY support either one or both versions of AES encryption, the KDC would create an RC4_HMAC_MD5 encryption key as well as create AES Keys for the account if msDS-SupportedEncryptionTypes was NULL or a value of 0. NoteYou do not need to apply any previous update before installing these cumulative updates. Environments without a common Kerberos Encryption type might have previously been functional due to automaticallyaddingRC4 or by the addition of AES, if RC4 was disabled through group policy by domain controllers. IMPORTANT We do not recommend using any workaround to allow non-compliant devices authenticate, as this might make your environment vulnerable. To mitigate this knownissue, open a Command Prompt window as an Administrator and temporarily use the following command to set theregistry key KrbtgtFullPacSignature to 0: NoteOnce this known issue is resolved, you should set KrbtgtFullPacSignature to a higher setting depending on what your environment will allow. It is a network service that supplies tickets to clients for use in authenticating to services. As we reported last week, updates released November 8 or later that were installed on Windows Server with the Domain Controller duties of managing network and identity security requests disrupted Kerberos authentication capabilities, ranging from failures in domain user sign-ins and Group Managed Service Accounts authentication to remote desktop connections not connecting. With this update, all devices will be in Audit mode by default: If the signature is either missing or invalid, authentication is allowed. If you have the issue, it will be apparent almost immediately on the DC. This can be done by Filtering the System Event log on the domain controllers for the following: Event Log: SystemEvent Source: Kerberos-Key-Distribution-CenterEvent IDs: 16,27,26,14,42NOTE: If you want to know about the detailed description, and what it means, see the section later in this article labeled: Kerberos Key Distribution Center Event error messages. Seehttps://go.microsoft.com/fwlink/?linkid=2210019tolearnmore. Prior to the November 2022 update, the KDC made some assumptions: After November 2022 Update the KDC Makes the following decisions: As explained above, the KDC is no longer proactively adding AES support for Kerberos tickets, and if it is NOT configured on the objects then it will more than likely fail if RC4_HMAC_MD5 has been disabled within the environment. 5020023 is for R2. KB5021131: How to manage the Kerberos protocol changes related to CVE-2022-37966. When I enter a Teams Room and want to use proximity join from the desktop app it does not work when my Teams users is in a different O365 tenant as the Teams Room device . After installing updates released on or after November 8, 2022 on your domain controllers, all devices must support AES ticket signing as required to be compliant with the security hardening required for CVE-2022-37967. This indicates that the target server failed to decrypt the ticket provided by the client. The Windows updates released on or after July 11, 2023 will do the following: Removes the ability to set value1for theKrbtgtFullPacSignaturesubkey. If the account does not have msds-SupportedEncryptionTypes set, or it is set to 0, domain controllers assume a default value of 0x27 (39) or the domain controller will use the setting in the registry key DefaultDomainSupportedEncTypes. If you have still pre Windows 2008/Vista Servers/Clients: An entire forest and all trusts should have a common Kerberos encryption type to avoid a likely outage. The initial deployment phase starts with the updates released on November 8, 2022 and continues with later Windows updates until theEnforcement phase. Explanation: The fix action for this was covered above in the FAST/Windows Claims/Compound Identity/Resource SID compression section. reg add "HKLM\\SYSTEM\\CurrentControlSet\\services\\kdc" /v ApplyDefaultDomainPolicy /t REG\_DWORD /d 0 /f ImportantStarting July 2023, Enforcement mode will be enabled on all Windows domain controllers and will block vulnerableconnections from non-compliant devices. If you still have RC4 enabled throughout the environment, no action is needed. If you want to include an AES256_CTS_HMAC_SHA1_96_SK (Session Key), then you would add 0x20 to the value. If this extension is not present, authentication is allowed if the user account predates the certificate. Running the following Windows PowerShell command to show you the list of objects in the domain that are configured for these. Printing that requires domain user authentication might fail. Supported values for ETypes: DES, RC4, AES128, AES256 NOTE: The value None is also supported by the PowerShell Cmdlet, but will clear out any of the supported encryption types. It was created in the 1980s by researchers at MIT. Explanation: If are trying to enforce AES anywhere in your environments, these accounts may cause problems. The accounts available etypes were 23 18 17. The Kerberos service that implements the authentication and ticket granting services specified in the Kerberos protocol. Windows Server 2008 R2 SP1: This update is not yet available but should be available in a week This update makes quality improvements to the servicing stack, which is the component that installs Windows updates. Kerberos replaced the NTLM protocol to be the default authentication protocol for domain connected devices on all Windows versions above Windows 2000. If you obtained a version previously, please download the new version. You do not need to install any update or make any changes to other servers or client devices in your environment to resolve this issue. For information about protocol updates, see the Windows Protocol topic on the Microsoft website. As noted in CVE-2020-17049, there are three registry setting values for PerformTicketSignature to control it, but in the current implementation you might encounter different issues with each setting.". Ensure that the target SPN is only registered on the account used by the server. This seems to kill off RDP access. Meanwhile businesses are getting sued for negligence for failing to patch, even if those patches might break more than they fix. More information on potential issues that could appear after installing security updates to mitigate CVE-2020-17049 can be found here. If the Users/GMSAs/Computers/Service accounts/Trust objects msDS-SupportedEncryptionTypes attribute was NULL (blank) or a value of 0, it defaults to an RC4_HMAC_MD5 encrypted ticket with AES256_CTS_HMAC_SHA1_96 session keys if the. People in your environment might be unable to sign into services or applications using Single Sign On (SSO) using Active Directory or in a hybrid Azure AD environment. Half of our domain controllers are updated, and about half of our users get a 401 from the backend server, and for the rest of the users, it is working as normal. If you find this error, you likely need to reset your krbtgt password. Adds PAC signatures to the Kerberos PAC buffer. Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type. The issue does not impact devices used by home customers and those that aren't enrolled in an on-premises domain. The Kerberos Key Distribution Center lacks strong keys for account: accountname. If yes, authentication is allowed. Microsoft released out-of-band emergency updates yesterday to fix the authentication issues, mentioning that the patches must be installed on all Domain Controllers in affected environments. "This is caused by an issue in how CVE-2020-17049 was addressed in these updates. After the entire domain is updated and all outstanding tickets have expired, the audit events should no longer appear. Microsoft began using Kerberos in Windows 2000 and it's now the default authorization tool in the OS. The next issue needing attention is the problem of mismatched Kerberos Encryption Types and missing AES keys. Microsoft is investigating a new known issue causing enterprise domain controllers to experience Kerberos authentication problems after installing security updates released to address CVE-2020-17049 during this month's Patch Tuesday, on November 10. Keep in mind the following rules/items: If you have other third-party Kerberos clients (Java, Linux, etc.) Though each of the sites were having a local domain controller before , due to some issues , these local DC's were removed and now the workstation from these sites are connected to the main domain controller . Client : /, The Key Distribution Center (KDC) encountered a ticket that did not contained the full PAC Signature. Or should I skip this patch altogether? One symptom is that from Server Manager (on my Windows 8.1 client) I get a "Kerberos authentication error" when trying to connect to the Hyper-V server or Essentials. Accounts that are flagged for explicit RC4 usage may be vulnerable. 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Richard Rich Descendants,