ADTRADE-007: BadSuccessor dMSA Migration Escalation Surface
- Platform
- Active Directory
- Category
- AD Adversary Tradecraft Indicators
- Severity
- Critical
- Zero Trust pillar
- Identity (weight 2)
- Golden fixtures
- 3
- Branch coverage
- Observed: fixtures prove the verdicts they exercise
- Provenance
- baseline
What it checks
Windows Server 2025 introduced delegated Managed Service Accounts (dMSA, object class msDS-DelegatedManagedServiceAccount) with a migration feature: a dMSA can be marked as superseding an existing account, after which it inherits that account's privileges and Kerberos keys. The 2024-disclosed 'BadSuccessor' technique abuses this: a principal that can merely CREATE a dMSA in an OU (CreateChild on the dMSA class, or broad write/GenericAll over the OU) can create one, point it at a privileged account, and inherit its keys — escalating to that account without ever holding rights over it directly. This check inventories OUs where a non-Tier-0 principal holds that capability.
Recommended value
No non-Tier-0 principal can create or write a delegated MSA (msDS-DelegatedManagedServiceAccount) in any OU.
Remediation
On each flagged OU, remove CreateChild (for the msDS-DelegatedManagedServiceAccount class), GenericAll, WriteDacl, and WriteOwner from non-administrative principals. Audit delegated OU permissions broadly — the same ACEs that enable BadSuccessor also enable other object-creation abuses. Until patched/mitigated, monitor creation of msDS-DelegatedManagedServiceAccount objects (4662/5137 events). This check SKIPs on forests whose schema predates Server 2025.
Fixture-proven verdicts
Every verdict below is proven by a golden fixture in the module's gating test suite. This table derives from the last green run; it cannot be edited by hand.
| Scenario | Expected verdict |
|---|---|
| clean | PASS |
| known-bad | FAIL |
| throttled | Not Assessed |
Framework mappings
- NIST SP 800-53
- AC-6, AC-3
- ANSSI
- vuln1_delegation_dmsa
- CIS AD Benchmark
- 6.3.1
- MITRE ATT&CK
- T1098, T1078.002