Understanding ESC1: Misconfigured Certificate Templates

What is ESC1?

ESC1 (Escalation via Certificate Services 1) is a vulnerability that occurs when certificate templates in AD CS are misconfigured with overly permissive enrollment rights. This misconfiguration allows low-privileged users to enroll in certificates that can be used for authentication, potentially leading to privilege escalation.

How ESC1 Works

The ESC1 attack typically follows these steps:

1. An attacker identifies a vulnerable certificate template with permissive enrollment rights.
2. The attacker, even with low privileges, enrolls in this template to obtain a certificate.
3. The obtained certificate can then be used for authentication, potentially granting elevated privileges.
4. With these elevated privileges, the attacker can perform further malicious actions, possibly leading to domain compromise.

Identifying Vulnerable Templates

Vulnerable templates often have one or more of the following characteristics:

• The "Enroll" permission is granted to low-privileged groups like "Authenticated Users" or "Domain Users".
• The template allows the requester to specify the Subject Alternative Name (SAN).
• The template has the "Client Authentication" Extended Key Usage (EKU).

Mitigating ESC1

To protect against ESC1, consider implementing the following measures:

Conclusion

ESC1 is a serious vulnerability that can have far-reaching consequences if exploited. By understanding how it works and implementing proper mitigation strategies, you can significantly enhance the security of your AD CS infrastructure.