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AUSCERT External Security Bulletin Redistribution
ESB-2021.3861.2
USN-5142-3: Samba regression update
14 December 2021
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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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