How a Misconfigured Active Directory Can Lead to Domain Admin

Active Directory (AD) remains one of the most important technologies in enterprise Windows environments—and one of the most attractive targets during internal penetration tests. In a recent discussion, penetration tester Spencer Allessie demonstrated how seemingly harmless Active Directory permissions can create an attack path that ultimately allows a standard user to impersonate a domain administrator and gain control of a domain controller. The demonstration focused on three major stages: Finding insecure Active Directory permissions Abusing Active Directory Certificate Services (AD CS) Escalating privileges to Domain Admin The techniques discussed are particularly important for organizations because they often originate from configuration mistakes rather than traditional software vulnerabilities. Active Directory: The Attack Often Starts With Permissions According to Spencer, one of the first things he looks for during an internal penetration test is misconfigured permissions. An attacker doesn't necessarily need administrator privileges at the beginning. Instead, the goal is to determine: What can the compromised user or one of their groups control? An ordinary domain user may have permissions over another group, computer, object, or certificate template. That permission can become a control path—a chain of permissions that allows an attacker to gradually increase their privileges. This is particularly dangerous in large environments where Active Directory has accumulated years of configuration changes, legacy permissions, and delegated administration. Finding Dangerous Delegations One of the tools demonstrated in the lab was ADDelegation, an Active Directory delegation management tool. The tool helps identify non-default delegations and makes it easier to identify potentially dangerous relationships between users, groups, and permissions. For example, the demonstration found that: Domain Users had permissions over a security group The group was called Template Managers Template Managers had the ability to manage certificate templates That immediately created an interesting attack path. The important question wasn't simply: "Does this permission look dangerous?" It was: "What can this permission allow us to control?" If an attacker compromises a user who belongs to a group with excessive permissions, that user may be able to manipulate other parts of the environment. You Don't Need a Domain Controller An important point from the demonstration is that many Active Directory enumeration tools don't need to run directly on a domain controller. A domain-joined workstation can be enough. As long as the compromised account can read Active Directory, an attacker or penetration tester can potentially enumerate information about: Users Groups Delegated permissions Certificate templates Domain objects Security relationships This is one reason why compromising an ordinary workstation can sometimes become the first step toward compromising an entire Windows domain. NetTools: Another Way to Find Dangerous Permissions The demonstration also introduced NetTools, described as a Swiss Army knife for Windows and Active Directory administrators. One useful feature is the ability to inspect trustee assignments and determine where particular users or groups have permissions. In the lab, the tool revealed that Template Managers had significant permissions. This is exactly the type of issue that internal penetration testers look for. The attacker isn't necessarily searching for a vulnerability like a buffer overflow. Instead, they're searching for legitimate permissions that have been configured incorrectly. This distinction is important. The Active Directory system may be working exactly as designed—the problem is that someone has given the wrong user or group too much control. From Permissions to AD CS The next stage of the attack involved Active Directory Certificate Services (AD CS). AD CS allows organizations to issue and manage digital certificates within Windows environments. Certificates can also be used for authentication. That makes certificate infrastructure extremely security-sensitive. If certificate templates are incorrectly configured, attackers may be able to manipulate them in ways that allow authentication as another user. The demonstration used a tool called Certify to inspect certificate templates and their permissions. One template of interest was a web server certificate template. At first glance, it didn't immediately appear vulnerable. It allowed the Template Managers group to enroll, but additional conditions were required before it could be abused for privilege escalation. Understanding ESC4 and ESC1 The attack chain demonstrated two important AD CS concepts: ESC4 ESC4 generally refers to situations where an attacker has excessive control over a certificate template. In this case, the compromised user could effectively influence the configuration of a certificate template through the permissions assigned to Template Managers. That doesn't automatically mean the attacker can become Domain Admin. However, it can provide the ability to modify the template into a configuration that becomes exploitable. ESC1 ESC1 involves a certificate template configuration that can allow a requester to specify an alternative identity, such as a different Subject Alternative Name (SAN), combined with client authentication capabilities and other conditions. In simplified terms: Misconfigured permissions → modify certificate template → request certificate for another identity → authenticate as that identity If the identity being impersonated is a Domain Admin, the consequences can be severe. Adding the Compromised User to the Dangerous Group The demonstration then showed an important consequence of having full control over the Template Managers group. If an attacker can modify group membership, they can potentially add their compromised account to the group. In the lab, the compromised user was Susie, an ordinary accounting user. After adding Susie to Template Managers, she inherited the group's permissions. This transformed a seemingly low-privileged account into an account capable of interacting with the certificate template infrastructure. This illustrates why excessive permissions on security groups are so dangerous. A group doesn't need to contain administrators to become dangerous. If the group itself controls something important, controlling membership in that group may be enough. Modifying the Certificate Template Once the attacker controls Template Managers, the next objective is to modify a certificate template. The demonstration looked for conditions that would allow the certificate to be used for authentication. Among the important configuration requirements were: Ability to supply an alternative subject/SAN Client authentication Appropriate enrollment permissions No manager approval or other restrictions that prevent the attack The attacker modifies the vulnerable template so that these conditions are satisfied. At that point, the certificate template can potentially be abused to impersonate another user. This is where the attack becomes particularly serious. Impersonating a Domain Administrator The demonstration then selected an account representing an IT administrator with Domain Admin privileges. A certificate was requested using that administrator's identity. The important concept is that the certificate isn't simply being used as a normal certificate. It becomes a mechanism for authentication. Because Windows environments can use certificates for Kerberos authentication, a properly crafted certificate can potentially allow an attacker to authenticate as the targeted account. The result is a dramatic privilege escalation: Standard user → certificate abuse → Domain Admin From Certificate to Domain Controller The demonstration then used a Kerberos-related tool to authenticate using the certificate. Once authentication succeeded, the attacker effectively had the identity of the Domain Admin account. The final proof of compromise was connecting to the domain controller through PowerShell Remoting and demonstrating that the session had Domain Admin privileges. At this stage, the attacker isn't simply compromising one computer. They potentially have control over the entire Active Directory domain. The Complete Attack Chain The demonstration can be simplified into the following attack path: Compromise standard user ↓ Enumerate Active Directory ↓ Find insecure permissions ↓ Control "Template Managers" group ↓ Add compromised user to the group ↓ Identify certificate template ↓ Modify vulnerable certificate template ↓ Create ESC1-style conditions ↓ Request certificate as Domain Admin ↓ Authenticate using certificate ↓ Obtain Domain Admin privileges ↓ Access the Domain Controller What makes this attack particularly interesting is that none of the individual steps necessarily looks catastrophic by itself. The danger comes from chaining them together. Why These Attacks Are So Dangerous According to Spencer, insecure Active Directory permissions and certificate-related weaknesses remain common findings during internal penetration tests. One reason is technical debt. Organizations frequently have Active Directory environments that have existed for many years. Certificate services may have been configured by: Former administrators External consultants Managed service providers IT teams that have since changed Administrators who didn't fully understand the security implications Over time, nobody may revisit the configuration. The result can be excessive permissions and vulnerable certificate templates sitting unnoticed in the environment. Why Security Tools May Not Immediately Detect It Another interesting aspect is detection. Offensive tools such as Certify and Kerberos-related tooling have become well known. Modern EDR and security products can often identify their signatures or behaviors. However, threat actors don't necessarily have to execute these tools directly on an endpoint. Attackers may use command-and-control infrastructure or other techniques to proxy activity into the environment. That can make detection considerably more difficult. Security teams therefore shouldn't rely solely on detecting a particular executable. They should also monitor the behavior associated with certificate abuse and unusual authentication. AD CS Should Be Treated as Critical Infrastructure One of the biggest lessons from the demonstration is that organizations need to treat their certificate infrastructure as a security-critical component. Security teams should regularly audit: Certificate templates Template permissions Enrollment permissions Certificate authorities Authentication settings Delegated administration Group memberships Template modification rights A certificate authority may appear to be just another piece of infrastructure, but certificates can ultimately provide authentication to highly privileged accounts. How Blue Teams Can Prioritize the Findings Not every vulnerability has the same impact. A penetration-testing report might contain: Critical High Medium Low severity findings. However, remediation shouldn't happen entirely in isolation. For example, changing a certificate template might affect infrastructure or applications that depend on it. Therefore, security teams should coordinate with the administrators responsible for: Active Directory PKI Windows infrastructure Virtualization Identity management Applications using certificates The goal should be to remove the attack path without accidentally breaking legitimate services. Defense: Reduce Excessive Permissions One of the most important defensive measures is least privilege. Organizations should regularly review: Who can modify security groups Who can modify certificate templates Who can enroll in certificates Which users belong to privileged groups Delegated Active Directory permissions Legacy permissions Nested group memberships A particularly important question is: "If this user is compromised, what can they control?" That's the perspective attackers use during internal penetration testing. Defense: Audit AD CS Organizations using Active Directory Certificate Services should regularly audit their certificate templates. Tools such as Locksmith can help security teams identify potentially dangerous AD CS configurations. The demonstration showed how a template that initially didn't appear obviously vulnerable could become exploitable after its permissions were modified. This is why certificate auditing shouldn't only focus on the current template configuration. Teams should also examine who has permission to modify that configuration. Is Active Directory Still Relevant? Despite frequent predictions that Active Directory is disappearing, the reality is different. Many organizations continue to operate significant on-premises Windows infrastructure. Hybrid identity environments are becoming increasingly common, but traditional Active Directory remains deeply embedded in enterprise environments. That means AD security skills continue to be valuable for both offensive and defensive security professionals. For penetration testers, this creates a large attack surface involving: Active Directory Windows authentication Kerberos Group Policy AD CS Identity management Privileged accounts Lateral movement Want to Become an Active Directory Pentester? Spencer's advice for people interested in penetration testing is not to immediately specialize in one area. Instead, experiment with different types of security testing. Platforms such as TryHackMe and Hack The Box can provide environments where beginners can explore: Web application security API security Linux Windows Active Directory Privilege escalation Red teaming Once you discover the area you enjoy most, you can specialize. For someone interested specifically in Windows and Active Directory penetration testing, Spencer highlighted certifications such as PNPT from TCM Security as a practical starting point, followed by CRTO from Zero Point Security for more advanced red-team and command-and-control concepts. The important point is that certifications are only part of the process. Hands-on practice is essential. Soft Skills Matter Too A common misconception about penetration testing is that the job is almost entirely hacking. In reality, consulting-based penetration testing involves much more: Client communication Reporting Project management Scheduling Explaining technical risks Presenting findings Working with infrastructure teams A technically brilliant penetration tester who cannot explain the business impact of a vulnerability may struggle to communicate the importance of their findings. Security leaders don't necessarily want to know every technical command used during an attack. They want to understand: What happened? How serious is it? What could an attacker do? What would the business impact be? How do we fix it? That's where strong communication becomes extremely valuable. The Bigger Lesson The most important takeaway from this demonstration isn't a particular tool or command. It's the concept of attack paths. A standard user doesn't need to be directly granted Domain Admin privileges for a domain to become compromised. Instead, an attacker may discover a chain such as: Low-privilege user → excessive group permissions → certificate template modification → certificate abuse → privileged authentication → Domain Admin Each individual permission might have been created for a legitimate reason. The problem occurs when those permissions can be chained together. This is why modern Active Directory security needs to focus not only on individual vulnerabilities, but on how permissions and identities interact across the entire environment. For defenders, the goal is to break those attack paths. For penetration testers, the goal is to find them before a real attacker does. And for anyone learning Windows security, Active Directory and AD CS are excellent areas to study because they demonstrate how seemingly small configuration mistakes can become complete domain compromise.