A Samba regression update has been released for Ubuntu Linux 18.04 LTS.

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Ubuntu Security Notice USN-5174-2
December 13, 2021

samba regression
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 18.04 LTS

Summary:

USN-5174-1 introduced a regression in Samba.

Software Description:
- samba: SMB/CIFS file, print, and login server for Unix

Details:

USN-5174-1 fixed vulnerabilities in Samba. Some of the 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.cgi?id=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 properly check sensitive
attributes. An authenticated attacker could possibly use this issue to
escalate privileges. (CVE-2020-25722)
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 18.04 LTS:
samba 2:4.7.6+dfsg~ubuntu-0ubuntu2.27

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

References:
  https://ubuntu.com/security/notices/USN-5174-2
  https://ubuntu.com/security/notices/USN-5174-1
  https://launchpad.net/bugs/1950363

Package Information:
  https://launchpad.net/ubuntu/+source/samba/2:4.7.6+dfsg~ubuntu-0ubuntu2.27