[USN-5174-2] Samba regression

========================================================================== Ubuntu Security Notice USN-5174-2 December 13, 2021
samba regression ==========================================================================
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: 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: 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: ubuntu.com/security/notices/USN-5174-2 ubuntu.com/security/notices/USN-5174-1 launchpad.net/bugs/1950363
Package Information: launchpad.net/ubuntu/+source/samba/2:4.7.6+dfsg~ubuntu-0ubuntu2.27