Is This Sid Taken? Varonis Hazard Labs Finds Synthetic Sid Shot Assault May 2026

For more detailed technical analysis, you can view the original research on the Varonis Blog .

Yes, identified a technique known as Synthetic SID Injection . For more detailed technical analysis, you can view

Standard security tools often monitor for changes to ACLs for existing users. Since the injection happens before the user exists, it can bypass traditional monitoring. Since the injection happens before the user exists,

An attacker with high privileges (but perhaps needing to maintain long-term, hidden access) adds a non-existent SID to a resource's ACL. Why This Matters The vulnerability relies on the

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

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".

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.