domain controllers Archives

Winsage

September 23, 2026

PAYLOAD ransomware hijacks Windows Group Policy in encryption-less attacks

A sophisticated PAYLOAD ransomware attack targeted an unnamed manufacturing organization in the Middle East, exploiting vulnerabilities in Microsoft Active Directory Group Policy. The attackers accessed the network through a compromised domain account via FortiGate SSL VPN on April 11, escalated privileges to domain administrator by April 13, and created a malicious Group Policy Object (GPO) named "PAYLOAD." This GPO was linked at the root of the domain, allowing it to affect nearly all domain-joined Windows workstations. The attackers distributed ransom notes, altered desktop images, displayed ransom messages at login, and disabled local administrator accounts. A second GPO, "win Firewall Off," was deployed to disable Windows Firewall across all profiles. The malicious policies activated on April 14 after systems were rebooted, causing widespread disruption. The attackers also exfiltrated data from file servers and published it on the dark web, while Kaspersky found no evidence of Windows file encryption or active malware processes. Recommendations for organizations include monitoring GPO creation, checking for unexpected changes, implementing multi-factor authentication for VPN access, and protecting privileged accounts.

Winsage

September 22, 2026

PAYLOAD ransomware hijacks Windows Group Policy in encryption-less attacks

A sophisticated PAYLOAD ransomware attack targeted a manufacturing organization in the Middle East, exploiting vulnerabilities in Microsoft Active Directory Group Policy. The attackers gained initial access on April 11 by compromising a domain account through the company's FortiGate SSL VPN. By April 13, they escalated privileges to a domain administrator and created a malicious Group Policy Object (GPO) named “PAYLOAD,” which was linked at the root of the domain. This GPO allowed them to distribute a ransom note, change desktop images, display a ransom message during login, and disable the local administrator account. A secondary GPO, “win Firewall Off,” was used to disable Windows Firewall across all profiles. The malicious changes activated on April 14 after system reboots, causing widespread disruption. The attackers also exfiltrated sensitive data, which was later released on the dark web. Kaspersky's investigation found no evidence of file encryption or active malware processes, indicating the attack was contained within Active Directory. Recommendations for organizations include monitoring GPO modifications, implementing multi-factor authentication for VPN access, and safeguarding privileged accounts.

Winsage

September 18, 2026

Windows 11 Update Can Break Active Directory Trust Relationships

A recent security update from Microsoft, KB5124008, has caused disruptions for organizations using on-premises Active Directory, particularly affecting domain-joined Windows 11 devices with Credential Guard. After installing this update, some devices lost their secure trust relationship with the domain, preventing users from logging in with valid credentials. The issue is linked to Machine Identity Isolation, a security feature that enhances machine account credential protection but requires domain controllers to operate at the Windows Server 2025 Domain Functional Level. Organizations that enabled this feature without meeting the prerequisite may experience trust relationship failures. Microsoft has suggested a workaround to disable Machine Identity Isolation and plans to suspend its enforcement in an upcoming update while improvements are made.

Winsage

September 17, 2026

Microsoft patch gives domain-joined Windows PCs trust issues

Microsoft acknowledged a significant issue affecting Windows 11 versions 24H2, 25H2, and 26H1 related to Active Directory domain logins as of September 16. This issue stems from changes made to Machine Identity Isolation in the September 2026 security update (KB5124008), which may cause Credential Guard-protected machine accounts to lose their secure channel with an on-premises Active Directory domain, preventing users from signing in with valid domain credentials. The update activates Machine Identity Isolation but does not enforce it immediately, and it is only compatible with environments linked to domain controllers operating at the Windows Server 2025 Domain Functional Level (DFL) or higher. Microsoft advised that devices not connected to Windows Server 2025 domain controllers will need to disable Machine Identity Isolation. A workaround involves disabling the feature through Intune, Group Policy, or the Windows Registry, followed by a device restart and repairing the secure channel using the Test-ComputerSecureChannel PowerShell command. Microsoft plans to address this issue in a future update by temporarily halting Machine Identity Isolation enforcement while enhancements are made.

Winsage

July 28, 2026

Proof-of-concept exploit released for Certighost Windows AD CS vulnerability

A proof-of-concept exploit for a vulnerability in Windows Active Directory Certificate Services (AD CS), identified as CVE-2026-54121, has emerged, allowing authenticated attackers to compromise an entire Windows domain. Microsoft addressed this vulnerability in its July 2026 security updates. The flaw enables attackers to manipulate machine account attributes, obtaining certificates to impersonate critical domain controllers and execute privileged Active Directory operations. Researchers H0j3n and Aniq Fakhrul discovered the vulnerability and publicly disclosed it with a functional exploit that exploits a fallback mechanism in AD CS. This exploit can automate the extraction of sensitive credentials through a DCSync attack. Microsoft has since implemented additional validation measures to enhance security against this vulnerability.

Winsage

July 16, 2026

Windows Netlogon Flaw CVE-2026-41089: CVSS 9.8 [2026]

CVE-2026-41089 is a critical vulnerability in the Windows Netlogon service, rated 9.8 on the CVSS scale, allowing unauthenticated attackers to execute arbitrary code with SYSTEM-level privileges on domain controllers. It affects all supported versions of Windows Server configured as domain controllers, from Windows Server 2012 R2 to the latest release. Microsoft addressed this vulnerability on May 12, 2026, during a broader update that included 138 fixes, but it went largely unnoticed until early June when active exploitation was confirmed. The vulnerability is characterized as a stack-based buffer overflow and is considered "wormable" due to its ability to self-propagate across systems without user intervention. Organizations are advised to patch all domain controllers and audit network access to mitigate exposure.

Winsage

June 1, 2026

Windows Server vulnerability can grant system privileges with just a malformed packet — domain controllers are being exploited in the wild

Microsoft is facing scrutiny due to a critical remote execution vulnerability, CVE-2026-41089, rated at 9.8, affecting Windows Server domain controllers from version 2012 onward. This vulnerability allows unauthenticated users on the same network to send malformed UDP packets to a domain controller, potentially granting unauthorized system access or causing a reboot, leading to denial-of-service scenarios. The vulnerable service is Netlogon, and there are no immediate mitigations available; patches will be released on May 12. The vulnerability could allow attackers to create multiple accounts with various access levels, compromising the security of entire networks. Cybersecurity experts recommend patching all linked domain controllers simultaneously. The vulnerability is caused by a buffer overflow in the Netlogon service due to a field in a network packet exceeding its expected size. A GitHub repository exists with proof-of-concept code that can crash the LSASS service. Additionally, Microsoft is in conflict with security researcher Chaotic Eclipse, who has published zero-day exploits following a breakdown in negotiations.

Winsage

June 1, 2026

Critical Windows Netlogon RCE flaw now exploited in attacks

The Centre for Cybersecurity Belgium (CCB) has warned about the exploitation of a critical vulnerability in Windows Netlogon, identified as CVE-2026-41089, which allows remote code execution on domain controllers without prior access or authentication. This vulnerability, characterized as a stack-based buffer overflow, was patched by Microsoft during the May 2026 Patch Tuesday. The CCB emphasized the urgency of patching vulnerable servers, noting that the vulnerability is actively being exploited. The CVSS score for this vulnerability is 9.8. Further details on the ongoing attacks have not been disclosed, and Microsoft has not updated its advisory on the vulnerability.

Winsage

May 28, 2026

Windows Server 2016 Update: Disastrous Bug Breaks AD

Microsoft released a mandatory patch (KB5087537) for Windows Server 2016 to enhance cryptographic layers and address critical vulnerabilities. This update is essential for organizations using legacy workloads, as mainstream support ended in January 2022, but extended support continues until January 12, 2027. The patch aims to prepare systems for the expiration of Windows Secure Boot certificates in June 2026, which, if not updated, could compromise security and expose systems to malware. The update uses a phased deployment model and includes a new SecureBoot folder to assist IT professionals in managing certificate status. It also addresses various quality-of-life issues, including bugs affecting Remote Desktop Connection and authentication errors with Microsoft services. However, a significant issue arises when the host server name is exactly 15 characters long, causing failures in the domain controller discovery process and obstructing critical operations. This bug is linked to the historical 15-character limit of NetBIOS, which affects the Active Directory lookup mechanism. Microsoft has acknowledged the issue but has not provided a timeline for a fix, leaving administrators to either rename servers or uninstall the update. As the Secure Boot deadline approaches, IT departments must carefully assess their environments to avoid disruptions while ensuring security compliance.

Winsage

May 25, 2026

How I Changed the SID on My Windows Server Without Reinstalling (And Why You Should Care)

Cloning a Windows Server machine can lead to issues with duplicate Security Identifiers (SIDs). A Security Identifier (SID) is a unique string assigned to every machine, user, and group in Windows, functioning like a fingerprint. Duplicate SIDs can cause problems such as domain join failures, incorrect WSUS reporting, inconsistent Group Policy application, and licensing issues. The author initially attempted to use sysprep to change the SID after cloning, which resulted in stripping the domain join and causing SQL Server to fail. The author then discovered Wittytool Disk Clone, which includes a SID changer that successfully generated a new SID and updated all necessary references without disrupting the server's configuration or applications. The process took only six minutes and worked similarly on Windows Server 2019. It is more efficient to generate a new SID during the cloning process rather than afterward. Important precautions include taking a snapshot or backup before making changes and being aware that changing the SID on domain controllers is more complex. Reactivation of Windows may also be required after the SID change.