Semperis adds detection for BadSuccessor flaw in Windows 2025

Cybersecurity firm Semperis has introduced new detection capabilities in its Directory Services Protector (DSP) platform, aiming to protect organisations against "BadSuccessor" — a newly disclosed privilege escalation technique in Windows Server 2025 that currently has no available patch.

The BadSuccessor flaw, revealed by researchers at Akamai, targets delegated Managed Service Accounts (dMSAs), a new Windows Server 2025 feature designed to enhance the security of service accounts. Instead, the researchers demonstrated how the feature can be exploited to impersonate highly privileged users in Active Directory, such as Domain Admins, without needing additional credentials or triggering alerts.

In direct response to Akamai's findings, Semperis worked with the researchers to develop and deploy new detection indicators within its DSP platform. The enhancements include one new Indicator of Exposure (IOE) and three Indicators of Compromise (IOCs), designed to help organisations identify early signs of potential abuse.

"Semperis moved quickly to translate the vulnerability into real-world detection capabilities for defenders, demonstrating how collaboration between researchers and vendors can lead to rapid, meaningful impact," said Yuval Gordon, Security Researcher at Akamai.

The detection indicators are focused on revealing abnormal behaviour around dMSAs, including excessive delegation rights, suspicious links between dMSAs and privileged accounts, and attempts to target sensitive credentials like the KRBTGT account. According to Semperis, this can give security teams a vital head start in identifying attacks before they can escalate.

"Service accounts remain one of the least governed yet most powerful assets in enterprise environments," said Tomer Nahum, Security Researcher at Semperis. "This collaboration with Akamai allowed us to close detection gaps fast and give defenders visibility into a deeply complex area of Active Directory that attackers continue to exploit."

The vulnerability has broad implications. Any organisation operating at least one domain controller (DC) running Windows Server 2025 may be at risk. According to Semperis, even a single misconfigured DC using dMSAs could expose the entire Active Directory environment to compromise.

As there is currently no fix for the vulnerability, Semperis is urging organisations to take immediate steps to protect their environments. These include auditing dMSA configurations, reviewing delegation permissions, and employing detection tools such as the updated DSP platform.

The new detection features aim to support defenders in closing a critical visibility gap. Service accounts, such as dMSAs, often run with elevated privileges but remain unmonitored or poorly managed in many enterprise environments. This lack of oversight creates a potential blind spot for attackers to exploit — a challenge the BadSuccessor technique highlights sharply.

Semperis stated that the DSP update is available now and is intended to offer a stopgap solution for organisations as they await official mitigation from Microsoft.

The case also serves as a reminder of the growing complexity of managing hybrid identity environments. With attackers increasingly targeting infrastructure such as Active Directory, new features — however well-intentioned — can quickly become unexpected attack vectors.

Gordon added, "The abuse of service accounts is a growing concern, and this high-profile vulnerability is a wake-up call."

Until a patch is released, security teams are advised to remain vigilant and proactive. By monitoring dMSA activity and understanding their configuration risks, organisations can reduce their exposure to what could otherwise be a silent but highly impactful method of privilege escalation.