An attacker with high privileges (but perhaps needing to maintain long-term, hidden access) adds a non-existent SID to a resource's ACL.
This attack involves threat actors with existing high privileges injecting "synthetic" into an Active Directory Access Control List (ACL) . This allows attackers to pre-assign permissions to a SID that does not yet exist in the environment, creating a silent "backdoor" that activates the moment a new account is created with that matching SID. Key Mechanics of the Attack An attacker with high privileges (but perhaps needing
A low-level account created later can suddenly "wake up" with Administrative or Domain Admin rights if those rights were pre-injected into the synthetic SID. Key Mechanics of the Attack A low-level account
Once a new user or group is created and assigned that specific SID, they automatically inherit all the "synthetic" permissions previously injected, often without appearing in standard audit logs as a new permission grant. Why This Matters Because the system allows adding SIDs that aren't
The vulnerability relies on the way Windows handles SID resolution. Because the system allows adding SIDs that aren't yet mapped to a user, the ACL essentially waits for its "missing half".