Versions Affected : All versions prior to FreeNAS 11.2-U8

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Description

All Samba versions 4.x.x before 4.9.17, 4.10.x before 4.10.11 and 4.11.x before 4.11.3 have an issue, where the S4U (MS-SFU) Kerberos delegation model includes a feature allowing for a subset of clients to be opted out of constrained delegation in any way, either S4U2Self or regular Kerberos authentication, by forcing all tickets for these clients to be non-forwardable.

In AD this is implemented by a user attribute delegation_not_allowed (aka not-delegated), which translates to disallow-forwardable. However the Samba AD DC does not do that for S4U2Self and does set the forwardable flag even if the impersonated client has the not-delegated flag set.

Workaround

No workaround is available.

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Mitigation

• Upgrade to FreeNAS 11.2-U8 or later

Commit

• FreeNAS Ports Tree Commit : e6f6c33
• Jira Ticket : NAS-104268

Further information

• 
• NIST CVE-2019-14870 Entry