Unconstrained Delegation
Unconstrained delegation
This a feature that a Domain Administrator can set to any Computer inside the domain. Then, anytime a user logins onto the Computer, a copy of the TGT of that user is going to be sent inside the TGS provided by the DC and saved in memory in LSASS. So, if you have Administrator privileges on the machine, you will be able to dump the tickets and impersonate the users on any machine.
So if a domain admin logins inside a Computer with "Unconstrained Delegation" feature activated, and you have local admin privileges inside that machine, you will be able to dump the ticket and impersonate the Domain Admin anywhere (domain privesc).
Automatically compromising a Print server
If an attacker is able to compromise a computer allowed for "Unconstrained Delegation", he could trick a Print server to automatically login against it saving a TGT in the memory of the server. Then, the attacker could perform a Pass the Ticket attack to impersonate the user Print server computer account.
Mitigation
Limit DA/Admin logins to specific services
Set "Account is sensitive and cannot be delegated" for privileged accounts.
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