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+++ This bug was initially created as a clone of Bug #2165827 +++

A paper by Tom Tervoort[1] noted that computing the PAC privsvr checksum over only the server checksum is vulnerable to collision attacks. In response, Microsoft has added a second KDC checksum over the full contents of the PAC[2].

This change will be required for PAC signatures to be accepted by AD from the 2023-07-11[3].

[1] https://i.blackhat.com/EU-22/Thursday-Briefings/EU-22-Tervoort-Breaking-Kerberos-RC4-Cipher-and-Spoofing-Windows-PACs-wp.pdf
[2] https://winprotocoldoc.blob.core.windows.net/productionwindowsarchives/MS-PAC/%5bMS-PAC%5d-20221212-diff.pdf
[3] https://support.microsoft.com/en-us/topic/kb5020805-how-to-manage-kerberos-protocol-changes-related-to-cve-2022-37967-997e9acc-67c5-48e1-8d0d-190269bf4efb

--- Additional comment from Julien Rische on 2023-01-31 08:50:37 UTC ---

The fix is available upstream:
https://github.com/krb5/krb5/pull/1284