domain controllers Archives

Winsage

May 5, 2026

April 2026 Windows Update Breaks Third-Party Backup Software by Blocking Vulnerable Driver

Microsoft will include the psmounterex.sys driver in its Vulnerable Driver Blocklist in the April 2026 security update, affecting third-party backup applications that use this driver for image mounting and Volume Shadow Copy Service (VSS) snapshots. This decision addresses CVE-2023-43896, a critical buffer overflow vulnerability. Affected software includes Macrium Reflect, Acronis Cyber Protect Cloud, UrBackup Server, and NinjaOne Backup on Windows 11, Windows 10, and Windows Server platforms. Users may face issues during image-mount operations, receiving error messages related to VSS timeouts and Code Integrity errors in the Event Viewer. To check if a system is affected, users can look for Event ID 3077 in the Code Integrity Operational log. Microsoft recommends upgrading to newer versions of backup applications that do not use blocked drivers and advises against uninstalling or delaying the April update. Additionally, the update may cause certain Windows Server 2025 devices to boot into BitLocker recovery mode and has led to out-of-band updates for Windows Server update failures and restart loops on domain controllers.

Winsage

April 21, 2026

Microsoft releases Windows Server update fix to fix its April update fixes

Microsoft has released an out-of-band update to fix a restart loop issue affecting certain Windows Server devices after the April 2026 update. The problem arose after installing the April 2026 Windows security update (KB5082063), causing domain controllers in multi-domain environments using Privileged Access Management (PAM) to experience LSASS crashes during startup, leading to repeated restarts and potential domain outages. The update targets Windows Server versions 2016 through 2025 and includes hotpatches for failed installations. Only Windows Servers were affected, while some enterprise devices may need to enter their BitLocker recovery key after the first restart post-installation. Microsoft has issued similar updates recently, raising concerns about the frequency of these occurrences.

Winsage

April 20, 2026

Emergency Update for Windows Server Following Reboot Issues

Microsoft has released emergency updates for various versions of Windows Server due to issues arising from the April 2026 Patch Tuesday security updates. A significant problem was a reboot loop affecting domain controllers caused by crashes of the Local Security Authority Subsystem Service (LSASS), which disrupted authentication services. This issue was especially problematic during the setup of new domain controllers. Additionally, some Windows Server 2025 systems encountered difficulties in installing the security update KB5082063. The out-of-band update (KB5091157) for Windows Server 2025 addresses both the installation failure and the domain controller restart issue. Other updates targeting the domain controller restart problem were released for additional supported Windows Server versions. Microsoft has introduced an out-of-band update for seven versions, including KB5091157 for Windows Server 2025 and KB5091571 for Windows Server, version 23H2. Furthermore, some Windows Server 2025 devices may boot into BitLocker recovery mode after the update, requiring users to enter a BitLocker recovery key.

Winsage

April 20, 2026

Microsoft releases emergency updates to fix Windows Server issues

Microsoft has confirmed that some administrators are experiencing difficulties installing the KB5082063 security update on Windows Server 2025. This month's Patch Tuesday updates have caused certain Windows servers, especially those with domain controller roles, to enter a restart loop due to failures in the Local Security Authority Subsystem Service (LSASS). Microsoft has released emergency out-of-band updates, including KB5091157 for Windows Server 2025, to address both the installation failure and the restart issues. Additionally, some Windows Server 2025 devices may boot into BitLocker recovery mode after installing the KB5082063 update. A bug affecting Windows Server 2019 and Windows Server 2022 that caused unexpected upgrades to Windows Server 2025 has also been resolved. Microsoft has issued various emergency updates throughout the year to address other issues, including a Bluetooth device visibility bug and vulnerabilities in the Routing and Remote Access Service (RRAS).

Winsage

April 18, 2026

Microsoft closes book on rogue Windows Server 2025 upgrades

Microsoft has officially resolved the incident involving the unexpected upgrade to Windows Server 2025, which occurred over a year ago and caused significant disruption for system administrators. The upgrade was automatic, with no rollback option, and was attributed to third-party products managing updates. Additionally, Microsoft's cumulative update KB5082063 has introduced new issues, causing LSASS crashes on non-Global Catalog domain controllers in environments using Privileged Access Management, leading to repeated restarts and potential inaccessibility of domains. Microsoft has acknowledged this problem and promised a resolution soon.

Winsage

April 17, 2026

Microsoft’s April patch puts Windows domain controllers into reboot loops — third known issue from KB5082063 is affecting Windows Server 2016 through 2025

Microsoft has acknowledged that the April 2026 security update for Windows Server, patch KB5082063, has caused significant disruptions for some enterprise domain controllers, leading to continuous reboot cycles in non-Global Catalog domain controllers used in Privileged Access Management (PAM) deployments. This has resulted in the unavailability of Active Directory authentication and directory services on affected servers. Additionally, the installation of KB5082063 may fail on some Windows Server 2025 systems. This issue marks the third consecutive year that April security updates have caused problems for Windows Server domain controllers. In previous years, Microsoft issued emergency fixes for similar issues, including crashes and complications with NTLM authentication. Administrators currently have limited options, including delaying the update, isolating a test domain controller, or engaging with Microsoft Support for tailored mitigation steps.

Winsage

January 27, 2026

Microsoft Phases Out RC4 in Kerberos to Boost Security

Microsoft is phasing out the RC4 encryption method used in Kerberos to address vulnerability CVE‑2026‑20833, which allows attackers to exploit weak encryption for offline cracking of service account passwords. The transition timeline includes an initial phase starting January 13, 2026, with new Kerberos audit events and optional registry controls to identify RC4 usage. In April 2026, domain controllers will default to AES‑SHA1, disabling fallback to RC4. By July 2026, Microsoft will remove Audit mode and enforce Enforcement mode, eliminating RC4 from the Kerberos protocol. Organizations are advised to update Active Directory Domain Controllers, monitor System event logs for new audit events, address KDCSVC events, and activate Enforcement mode to enhance security against RC4-related vulnerabilities.

Winsage

December 19, 2025

Microsoft Phases Out RC4 Encryption by 2026 to Bolster Windows Security

Microsoft has announced the phased discontinuation of the RC4 encryption cipher, with full implementation expected by mid-2026. RC4, created in 1987, has been increasingly recognized as a vulnerability, exploited in various high-profile cyberattacks. Microsoft plans to disable RC4 by default in Windows Kerberos authentication, encouraging organizations to transition to more secure alternatives like AES-256. This decision follows years of warnings from the cybersecurity community and aims to eliminate long-standing cryptographic weaknesses. The transition will require organizations to audit and upgrade their infrastructures, as many legacy applications still depend on RC4. Disabling RC4 is expected to reduce the success rates of attacks exploiting weak encryption. Microsoft has introduced tools to help administrators identify hidden RC4 usage. The change reflects a commitment to zero-trust architectures and aligns with recommendations from organizations like NIST. Experts recommend a multi-step approach for organizations to navigate this transition effectively.

Winsage

December 10, 2025

Beyond RC4 for Windows authentication

Two new PowerShell scripts from the Microsoft Kerberos-Crypto GitHub repository have been introduced to enhance cybersecurity by streamlining the monitoring of Security Event logs on domain controllers. 1. List-AccountKeys.ps1: This script queries the Security Event Log for the Keys field, enumerating the keys associated with accounts in the event logs. It provides details such as the timestamp, account name, account type, and specific account keys. For example, it can show that accounts have access to keys like RC4, AES128-SHA96, AES256-SHA96, and AES128-SHA256. 2. Get-KerbEncryptionUsage.ps1: This script allows users to query events to determine which encryption types Kerberos utilized, revealing requests that employed AES256-SHA96. It also offers filtering options for specific encryption algorithms, such as RC4. Organizations can further enhance their security by using SIEM solutions like Microsoft Sentinel or built-in Windows event forwarding to query these logs.

Tech Optimizer

November 13, 2025

Emotet: The horse returns to a gallop more dangerous than ever

Emotet is a Trojan Horse malware that emerged in 2014, impacting over 1.6 million devices and originally designed to steal banking credentials. Developed by the MealyBug criminal organization, it evolved into a modular Trojan-dropper, enabling it to download various payloads and act as Malware-as-a-Service on the dark web. Emotet spreads primarily through spam emails, often using malicious Word or Excel files, and has been disseminated via local area networks and password-protected zip folders. The malware operates through botnets categorized into epochs, with Epochs 1, 2, and 3 dismantled in 2021 by a coordinated international operation. Following this, Emotet resurfaced in November 2021 as Epochs 4 and 5, incorporating a Cobalt Strike beacon for enhanced propagation. Recommended precautions include keeping software updated, using two-factor authentication, and educating employees about email threats. Network administrators are advised to block unscannable email attachments, configure specific email filters, and maintain secure backups.