Attachment 17647 Details for Bug 15231 – Draft advisory without versions (v2)

Draft advisory without versions (v2)

CVE-2022-45142-KrbtgtFullPacSignature-v02.txt (text/plain), 2.51 KB, created by Andrew Bartlett on 2022-11-14 02:06:24 UTC

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Creator: Andrew Bartlett

Created: 2022-11-14 02:06:24 UTC

Size: 2.51 KB

patch

obsolete

>===========================================================
>== Subject:     Kerberos constrained delegation ticket
>==              forgery possible against Samba AD DC
>==
>== CVE ID#:     CVE-2022-45142 (MS CVE-2022-37967)
>==
>== Versions:    All versions of the Samba AD DC
>==
>== Summary:     This is the Samba CVE for the Windows
>==              Kerberos Elevation of Privilege Vulnerability
>==		disclosed by Microsoft on Nov 8 2022.
>==
>==              A service account with the special constrained
>==              delegation permission could forge a more powerful
>==              ticket than the one it was presented with.
>===========================================================
>
>===========
>Description
>===========
>
>Kerberos constrained delegation, known also as S4U2Proxy, requires
>that the intermediate service present to the KDC a valid Kerberos
>ticket obtained by the user as evidence that they had authenticated,
>so that a new ticket can be issued for the target server.
>
>This ticket is signed in multiple stages, but the important protection
>of the SID list is done first with the server's key, and then with the
>krbtgt key over that result. 
>
>However HMAC-MD5 is weak in 2022, and given that the intermediate
>server knows its own password and can set it to arbitrary values, it
>is feasible to brute force a new server checksum that matches the
>value already signed by the krbtgt key, but including a privileged
>group.
>
>==================
>Patch Availability
>==================
>
>Patches addressing both these issues have been posted to:
>
>    https://www.samba.org/samba/security/
>
>Additionally, Samba $VERSIONS have been issued
>as security releases to correct the defect.  Samba administrators are
>advised to upgrade to these releases or apply the patch as soon
>as possible.
>
>==================
>CVSSv3 calculation
>==================
>
>CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H (6.6)
>
>However, please note that Microsoft's score, which is normally lower
>than Samba for the same issue, scores this as:
>
>CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H (7.2)
>
>==========
>Workaround
>==========
>
>Disable delegation for services that are not fully trusted.
>
>=======
>Credits
>=======
>
>Originally reported to Microsoft and released as CVE-2022-37967.
>
>Advisory written by Andrew Bartlett of Catalyst and the Samba Team.
>
>Patches provided by Joseph Sutton of Catalyst and the Samba Team.
>
>==========================================================
>== Our Code, Our Bugs, Our Responsibility.
>== The Samba Team
>==========================================================
>

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