Operating System:

[Ubuntu]

Published:

14 December 2021

Protect yourself against future threats.

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             AUSCERT External Security Bulletin Redistribution

                              ESB-2021.3861.2
                    USN-5142-3: Samba regression update
                             14 December 2021

===========================================================================

        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           Samba
Publisher:         Ubuntu
Operating System:  Ubuntu
Impact/Access:     Increased Privileges           -- Existing Account      
                   Denial of Service              -- Existing Account      
                   Provide Misleading Information -- Existing Account      
                   Reduced Security               -- Remote/Unauthenticated
                   Unauthorised Access            -- Existing Account      
Resolution:        Patch/Upgrade
CVE Names:         CVE-2021-23192 CVE-2021-3738 CVE-2021-3671
                   CVE-2020-25722 CVE-2020-25721 CVE-2020-25719
                   CVE-2020-25718 CVE-2020-25717 CVE-2016-2124

Reference:         ESB-2021.3774

Original Bulletin: 
   https://ubuntu.com/security/notices/USN-5142-3

Revision History:  December 14 2021: Vendor released regression update
                   November 12 2021: Initial Release

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USN-5142-3: Samba regression
13 December 2021

USN-5142-1 introduced a regression in Samba.
Releases

  o Ubuntu 21.10
  o Ubuntu 21.04
  o Ubuntu 20.04 LTS

Packages

  o samba - SMB/CIFS file, print, and login server for Unix

Details

USN-5142-1 fixed vulnerabilities in Samba. Some of the upstream changes
introduced a regression in Kerberos authentication in certain environments.

Please see the following upstream bug for more information:
https://bugzilla.samba.org/show_bug.cgiid=14922

This update fixes the problem.

Original advisory details:

Stefan Metzmacher discovered that Samba incorrectly handled SMB1 client
connections. A remote attacker could possibly use this issue to downgrade
connections to plaintext authentication. ( CVE-2016-2124 )

Andrew Bartlett discovered that Samba incorrectly mapping domain users to
local users. An authenticated attacker could possibly use this issue to
become root on domain members. ( CVE-2020-25717 )

Andrew Bartlett discovered that Samba did not correctly sandbox Kerberos
tickets issues by an RODC. An RODC could print administrator tickets,
contrary to expectations. ( CVE-2020-25718 )

Andrew Bartlett discovered that Samba incorrectly handled Kerberos tickets.
Delegated administrators could possibly use this issue to impersonate
accounts, leading to total domain compromise. ( CVE-2020-25719 )

Andrew Bartlett discovered that Samba did not provide stable AD
identifiers to Kerberos acceptors. ( CVE-2020-25721 )

Andrew Bartlett discovered that Samba did not properly check sensitive
attributes. An authenticated attacker could possibly use this issue to
escalate privileges. ( CVE-2020-25722 )

Stefan Metzmacher discovered that Samba incorrectly handled certain large
DCE/RPC requests. A remote attacker could possibly use this issue to
bypass signature requirements. ( CVE-2021-23192 )

William Ross discovered that Samba incorrectly handled memory. A remote
attacker could use this issue to cause Samba to crash, resulting in a
denial of service, or possibly escalate privileges. ( CVE-2021-3738 )

Joseph Sutton discovered that Samba incorrectly handled certain TGS
requests. An authenticated attacker could possibly use this issue to cause
Samba to crash, resulting in a denial of service. ( CVE-2021-3671 )

The fix for CVE-2020-25717 results in possible behaviour changes that could
affect certain environments. Please see the upstream advisory for more
information:

https://www.samba.org/samba/security/ CVE-2020-25717 .html

Update instructions

The problem can be corrected by updating your system to the following package
versions:

Ubuntu 21.10

  o samba - 2:4.13.14+dfsg-0ubuntu0.21.10.4

Ubuntu 21.04

  o samba - 2:4.13.14+dfsg-0ubuntu0.21.04.4

Ubuntu 20.04

  o samba - 2:4.13.14+dfsg-0ubuntu0.20.04.4

In general, a standard system update will make all the necessary changes.

References

  o https://launchpad.net/bugs/1950363

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