In recent weeks, the cybersecurity landscape for enterprise Windows deployments has been shaken by the disclosure of a new zero-day vulnerability in Active Directory—dubbed "BadSuccessor." Security forums, tech news outlets, and IT administrators across the globe are keenly following developments related to this flaw, which specifically impacts environments with at least one Windows Server 2025 domain controller. While BadSuccessor is not yet widespread, the risks associated with it are potentially severe, especially for organizations looking to adopt the latest server technology from Microsoft.
BadSuccessor was discovered by Yuval Gordon, a security researcher at Akamai, who published the initial analysis and detection guidelines on May 21. The flaw, whose technical details quickly spread through professional and open-source security communities, is a zero-day privilege escalation vulnerability. This means a malicious actor who gains exploitation capability can elevate their rights within Active Directory, possibly leading to full domain or even forest compromise.
Akamai’s disclosure noted the vulnerability exists not within longstanding account types, but rather in the newly introduced delegated Managed Service Accounts (dMSAs) in Windows Server 2025. These accounts were intended to facilitate the migration of legacy and non-managed service accounts to a more secure, manageable framework. Ironically, it is within this very pathway to increased security that a fundamental weakness was uncovered.
The danger arises if a threat actor compromises such an account through phishing, brute force, credential theft, or by chaining lesser vulnerabilities. From there, they could create or manipulate a dMSA to inherit elevated privileges. Once this occurs, standard escalation techniques within Active Directory could be used to eventually compromise the entire domain or even cascade to other trusted domains and forests.
Industry watchdogs and security vendors moved quickly to fill the gap. Akamai’s blog provides not only a detection guide but also initial mitigation strategies for Active Directory administrators. Tenable, for instance, has introduced an "Indicator of Exposure" (IoE) for BadSuccessor in version 3.95 of its Identity Exposure platform, allowing organizations to scan and monitor their AD environments for symptoms or indicators tied to exploitation attempts.
Nonetheless, the existence of public proof-of-concept (PoC) code sharply heightens the risk. Multiple implementations, including a .NET tool called SharpSuccessor, as well as modules in NetExec (successor to CrackMapExec) and BloodyAD, are now circulating on GitHub and offensive security tool repositories. This ready availability means that attackers with even moderate skill can attempt to exploit BadSuccessor in unpatched or misconfigured environments shortly after its disclosure.
Industry analysts point out that this pattern is unsurprising; the introduction of new service account paradigms—like dMSAs—often leads to unforeseen gaps during the first months of live deployment. However, the open and collaborative nature of the disclosure, coupled with rapid development of detection and mitigation tooling, is a positive indicator that the security community is increasingly vigilant and well-equipped to handle such incidents.
For managed service providers, large financial institutions, and governments—entities that often lead the charge on new Microsoft infrastructure releases—the prudent move is to adopt preventative controls and staff awareness immediately. Small and midsize businesses may have more breathing room, but should nonetheless monitor update and patch channels closely.
Additionally, while no in-the-wild exploitation has been confirmed as of June 2, this assessment relies on voluntary reporting and sample telemetry. Given the track record of threat actors, it may only be a matter of time before more aggressive campaigns appear. Security researchers should remain vigilant for any early signals of widespread abuse.
As the cybersecurity world waits for Microsoft’s official patch, the episode showcases the advantages of an engaged research community, transparent vendor communication, and rapid third-party response. But it also exposes persistent challenges: complexity, privilege abuse, and the ever-present lag between new feature release and downstream hardening.
Organizations considering or already running Windows Server 2025 must act now—not only to protect themselves from BadSuccessor but to future-proof their environments against the next wave of identity-centric attacks. By fostering a proactive culture of security, regular auditing, and community collaboration, enterprise Windows shops can stay one step ahead of attackers—and ensure that the successor to every innovation is not a “bad” one, but a secured, resilient foundation for business success.
Source: Security Boulevard Frequently Asked Questions About BadSuccessor
BadSuccessor was discovered by Yuval Gordon, a security researcher at Akamai, who published the initial analysis and detection guidelines on May 21. The flaw, whose technical details quickly spread through professional and open-source security communities, is a zero-day privilege escalation vulnerability. This means a malicious actor who gains exploitation capability can elevate their rights within Active Directory, possibly leading to full domain or even forest compromise.Akamai’s disclosure noted the vulnerability exists not within longstanding account types, but rather in the newly introduced delegated Managed Service Accounts (dMSAs) in Windows Server 2025. These accounts were intended to facilitate the migration of legacy and non-managed service accounts to a more secure, manageable framework. Ironically, it is within this very pathway to increased security that a fundamental weakness was uncovered.
Understanding the Technical Underpinnings
The security risk centers on how dMSAs are managed within Active Directory. There are two primary vectors by which BadSuccessor can be exploited:- Creation vector: A user account with permission to create a new dMSA (
msDS-DelegatedManagedServiceAccountobject class) in any container or organizational unit (OU) can trigger the vulnerability. - Abuse of existing dMSA: A user who can modify the
msDS-ManagedAccountPrecededByLinkattribute of any existing dMSA can also leverage the flaw for privilege escalation.
How the Exploit Works in Practice
To perform a successful exploitation, an attacker must possess access to an account with sufficient Active Directory permissions. The specific actions—namely, the creation or modification of dMSAs or their key attributes—would likely fall within the purview of administrative users, delegated service account operators, or users with bespoke permissions for service account management.The danger arises if a threat actor compromises such an account through phishing, brute force, credential theft, or by chaining lesser vulnerabilities. From there, they could create or manipulate a dMSA to inherit elevated privileges. Once this occurs, standard escalation techniques within Active Directory could be used to eventually compromise the entire domain or even cascade to other trusted domains and forests.
Current Status: Patches, Detection, and Reporting
As of the most recent June 2 updates, Microsoft has neither released an official patch nor assigned a CVE identifier to BadSuccessor. This is not unusual for newly discovered zero-days, especially those that emerge in newly released products or features. Microsoft, as the CVE Numbering Authority (CNA) for its software, typically issues advisories and patches following internal validation and remediation development—a process that can take weeks or more, even in the face of active threats.Industry watchdogs and security vendors moved quickly to fill the gap. Akamai’s blog provides not only a detection guide but also initial mitigation strategies for Active Directory administrators. Tenable, for instance, has introduced an "Indicator of Exposure" (IoE) for BadSuccessor in version 3.95 of its Identity Exposure platform, allowing organizations to scan and monitor their AD environments for symptoms or indicators tied to exploitation attempts.
Real-World Impact and Prevalence
The practical risk profile of BadSuccessor, while severe in affected instances, is tempered by a key factor: as of early June, only around 0.7% of all Active Directory domains sampled by Tenable’s telemetry data include at least one Windows Server 2025 domain controller. Other third-party estimates suggest similarly low—but rising—adoption rates, as enterprises typically lag in deploying cutting-edge domain controllers until after a period of proven stability and patch maturity.Nonetheless, the existence of public proof-of-concept (PoC) code sharply heightens the risk. Multiple implementations, including a .NET tool called SharpSuccessor, as well as modules in NetExec (successor to CrackMapExec) and BloodyAD, are now circulating on GitHub and offensive security tool repositories. This ready availability means that attackers with even moderate skill can attempt to exploit BadSuccessor in unpatched or misconfigured environments shortly after its disclosure.
How Did BadSuccessor Get Its Name?
According to Yuval Gordon, the vulnerability’s moniker comes from the notion that the exploited service account or dMSA becomes a "bad successor," inheriting inappropriate privileges from other accounts in a manner the original Active Directory designers clearly did not intend. The name resonates with the overall risk—a service pathway intended for smoother, safer account management becomes a silent carrier of highly privileged compromise.Proof-of-Concepts and Offensive Security Tooling
One of the biggest concerns around new vulnerabilities, particularly zero-days, is the speed with which attackers can operationalize them. In the case of BadSuccessor, this timeline has been worryingly short. Within days of disclosure, working exploitation scripts and frameworks appeared on GitHub:- SharpSuccessor: A .NET implementation that demonstrates and automates the necessary steps to leverage BadSuccessor within a target Active Directory environment.
- NetExec integration: This is notable as NetExec is an updated take on the widely infamous CrackMapExec—a staple of red teamers and penetration testers for years. The addition of a BadSuccessor module means the flaw becomes widely accessible to those with minimal coding skills.
- BloodyAD support: A framework focused on Active Directory privilege escalation also now includes modules targeting the dMSA-related misconfiguration and vulnerabilities laid bare by BadSuccessor.
Mitigation Strategies: What Can Organizations Do Now?
With no official patch as of early June, enterprise defenders have to focus on "defense-in-depth" and interim mitigation strategies:- Audit permissions for dMSA creation: Restrict the ability to create or modify delegated Managed Service Accounts to only the most essential administrators. Use group policy, access control lists, and other AD governance mechanisms to ensure strict permission boundaries.
- Monitor for suspicious dMSA activity: Employ dedicated SIEM tools or vendor products such as Tenable Identity Exposure to flag anomalous activity around dMSAs or the creation/modification of the msDS-DelegatedManagedServiceAccount class or its associated attributes.
- Limit exposure of privileged accounts: Implement least privilege principles, monitor domain controllers for abnormal operations, and rapidly respond to suspected attempts to escalate rights.
- Isolate Windows Server 2025 domain controllers: Where feasible, keep these new DCs within tightly controlled subnetworks or test domains until comprehensive patches and hardening guides are available.
The Industry's Response and Future Patch Outlook
Both Akamai and Tenable have published in-depth advisories, including guidance for mitigation and detection. Microsoft, for its part, has acknowledged the issue and publicly committed to releasing a fix in future updates, but as of this writing, no date has been set and no CVE number has been announced.Industry analysts point out that this pattern is unsurprising; the introduction of new service account paradigms—like dMSAs—often leads to unforeseen gaps during the first months of live deployment. However, the open and collaborative nature of the disclosure, coupled with rapid development of detection and mitigation tooling, is a positive indicator that the security community is increasingly vigilant and well-equipped to handle such incidents.
Assessing The Broader Risk: Who Should Be Concerned?
While the publicity around BadSuccessor has inevitably led to some breathless media coverage, a sober analysis reveals the flaw is currently most pressing for organizations at the forefront of Active Directory innovation. If you have not yet deployed Windows Server 2025 domain controllers, you are not exposed. However, the presence of public exploits means that as adoption rises—and especially as organizations begin side-by-side domain upgrades—attackers will increasingly probe for vulnerable environments.For managed service providers, large financial institutions, and governments—entities that often lead the charge on new Microsoft infrastructure releases—the prudent move is to adopt preventative controls and staff awareness immediately. Small and midsize businesses may have more breathing room, but should nonetheless monitor update and patch channels closely.
Open Questions and Unverifiable Claims
There are, inevitably, aspects of BadSuccessor where caution is warranted. Because the root technical flaw involves both newly designed service account logic and complex AD permissioning, it is possible further variants of this attack will emerge—potentially affecting configurations not yet imagined by current testers.Additionally, while no in-the-wild exploitation has been confirmed as of June 2, this assessment relies on voluntary reporting and sample telemetry. Given the track record of threat actors, it may only be a matter of time before more aggressive campaigns appear. Security researchers should remain vigilant for any early signals of widespread abuse.
Comparing BadSuccessor to Other Recent Active Directory Threats
The discovery of privilege escalation flaws in AD is certainly nothing new. However, BadSuccessor stands out in several ways:- Targeting of new features: The vulnerability affects a credential model that was deliberately designed to improve account management security.
- Attack scope: Unlike many recent AD flaws contingent on full domain controller upgrades or forest functional level changes, BadSuccessor requires only a single Windows Server 2025 DC—lowering the bar for real-world exploitation.
- Speed of community response: The presence of working PoCs and detection logic within days of disclosure is remarkable and reflects both the increased urgency and coordinated response of the security industry.
Recommendations for Next Steps
For Active Directory and Windows Server administrators, the following action checklist is recommended:- Inventory and classify all domain controllers running Windows Server 2025.
- Review permissions for all users and service accounts with dMSA creation or modification rights.
- Deploy detection rules for anomalous activity tied to dMSA creation or attribute modification, using available guidance from Tenable, Akamai, and vendor partners.
- Engage stakeholders across security operations, incident response, and executive leadership on the evolving risk profile.
- Prepare for rapid patch deployment as soon as Microsoft releases a fix; interim monitoring should remain active in the weeks and months ahead.
- Contribute to or monitor public community forums and advisories for updates, threat intel, and clarification on defensive posture as research continues.
Conclusion: Lessons from BadSuccessor for the Future of Active Directory Security
The BadSuccessor vulnerability is a timely reminder that new features, while offering undeniable advancements in manageability and security, can also introduce unforeseen vulnerabilities. The critical takeaway for WindowsServer and Active Directory administrators is that innovation must always be balanced by rigorous, defense-in-depth controls and that no “set-it-and-forget-it” posture is viable for such mission-critical infrastructure.As the cybersecurity world waits for Microsoft’s official patch, the episode showcases the advantages of an engaged research community, transparent vendor communication, and rapid third-party response. But it also exposes persistent challenges: complexity, privilege abuse, and the ever-present lag between new feature release and downstream hardening.
Organizations considering or already running Windows Server 2025 must act now—not only to protect themselves from BadSuccessor but to future-proof their environments against the next wave of identity-centric attacks. By fostering a proactive culture of security, regular auditing, and community collaboration, enterprise Windows shops can stay one step ahead of attackers—and ensure that the successor to every innovation is not a “bad” one, but a secured, resilient foundation for business success.
Source: Security Boulevard Frequently Asked Questions About BadSuccessor