Robbie Harwood rharwood at
Tue Nov 17 12:16:20 EST 2020

Luke Hebert <lhebert at> writes:

> Hi,
> We've just started encountering problems at customer sites with Kerberos
> enabled clients as a result of how Microsoft appears to be approaching
> CVE-2020-17049
> <>. The
> details on this CVE are slim on Mitre and there is a small amount of
> additional information on the microsoft portal. I thought I'd ask the list
> what their thoughts are on what is being done here. Disabling service
> ticket and tgt renewability is not great and it obviously breaks long
> running processes that rely on renewability of these items. I'm sure we
> could move to an alternate approach where we do not renew these items but
> rather obtain a new one but the changes are likely non-trivial across many
> different projects.
>>> *How does this patch affect third-party Kerberos clients?*
>>> When the registry key is set to 1, patched domain controllers will issue
> service tickets and Ticket-Granting Tickets (TGT)s that are not renewable
> and will refuse to renew existing service tickets and TGTs. Windows clients
> are not impacted by this since they never renew service tickets or TGTs.
> Third-party Kerberos clients may fail to renew service tickets or TGTs
> acquired from unpatched DCs. If all DCs are patched with the registry set
> to 1, third-party clients will no longer receive renewable tickets.

You're correct that Microsoft has not released details on this issue.

They have indicated that some failures are a known issue, and claim to
be working on a fix:

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