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Critical Golden dMSA Attack in Windows Server 2025 Enables Cross-Domain Attacks and Persistent Access. Cybersecurity researchers have disclosed what they say is a "critical design flaw" in delegated Managed Service Accounts (dMSAs) introduced in Windows Server 2025. "The flaw can result in high-impact attacks, enabling cross-domain lateral movement and persistent access to all managed service accounts and their resources across Active Directory indefinitely," Semperis said in a report shared with The Hacker News. Put differently, successful exploitation could allow adversaries to sidestep authentication guardrails and generate passwords for all Delegated Managed Service Accounts (dMSAs) and group Managed Service Accounts (gMSAs) and their associated service accounts. The persistence and privilege escalation method has been codenamed Golden dMSA, with the cybersecurity company deeming it as low complexity owing to the fact that the vulnerability simplifies brute-force password generation. However, in order for bad actors to exploit it, they must already be in possession of a Key Distribution Service (KDS) root key that's typically only available to privileged accounts, such as root Domain Admins, Enterprise Admins, and SYSTEM. Described as the crown jewel of Microsoft's gMSA infrastructure, the KDS root key serves as a master key, allowing an attacker to derive the current password for any dMSA or gMSA account without having to connect to the domain controller. "The attack leverages a critical design flaw: A structure that's used for the password-generation computation contains predictable time-based components with only 1,024 possible combinations, making brute-force password generation computationally trivial," security researcher Adi Malyanker said. Delegated Managed Service Accounts is a new feature introduced by Microsoft that facilitates migration from an existing legacy service account. It was introduced in Windows Server 2025 as a way to counter Kerberoasting attacks. The machine accounts bind authentication directly to explicitly authorized machines in Active Directory (AD), thus eliminating the possibility of credential theft. By tying authentication to device identity, only specified machine identities mapped in AD can access the account. Golden dMSA, similar to Golden gMSA Active Directory attacks, plays out over four steps once an attacker has obtained elevated privileges within a domain - "This process requires no additional privileged access once the KDS root key is obtained, making it a particularly dangerous persistence method," Malyanker said. "The attack highlights the critical trust boundary of managed service accounts. They rely on domain-level cryptographic keys for security. Although automatic password rotation provides excellent protection against typical credential attacks, Domain Admins, DnsAdmins, and Print Operators can bypass these protections entirely and compromise all of the dMSAs and gMSAs in the forest." Semperis noted that the Golden dMSA technique turns the breach into a forest-wide persistent backdoor, given that compromising the KDS root key from any single domain within the forest is enough to breach every dMSA account across all domains in that forest. In other words, a single KDS root key extraction can be weaponized to achieve cross-domain account compromise, forest-wide credential harvesting, and lateral movement across domains using the compromised dMSA accounts. "Even in environments with multiple KDS root keys, the system consistently uses the first (oldest) KDS root key for compatibility reasons," Malyanker pointed out. "This means that the original key we've compromised could be preserved by Microsoft's design – creating a persistent backdoor that could last for years." Even more concerning is that the attack completely sidesteps normal Credential Guard protections, which are used to secure NTLM password hashes, Kerberos Ticket Granting Tickets (TGTs), and credentials so that only privileged system software can access them. Following responsible disclosure on May 27, 2025, Microsoft said, "If you have the secrets used to derive the key, you can authenticate as that user. These features have never been intended to protect against a compromise of a domain controller." Semperis has also released an open-source as proof-of-concept (PoC) to demonstrate the attack. "What starts as one DC compromise escalates to owning every dMSA-protected service across an entire enterprise forest," Malyanker said. "It's not just privilege escalation. It's enterprise-wide digital domination through a single cryptographic vulnerability."