A SSSD security update has been released for Ubuntu Linux 18.04 LTS, 20.04 LTS, and 21.04.

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Ubuntu Security Notice USN-5067-1
September 08, 2021

sssd vulnerabilities
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 21.04
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS

Summary:

Several security issues were fixed in sssd.

Software Description:
- sssd: System Security Services Daemon

Details:

Jakub Hrozek discovered that SSSD incorrectly handled file permissions. A
local attacker could possibly use this issue to read the sudo rules
available for any user. This issue only affected Ubuntu 18.04 LTS.
(CVE-2018-10852)

It was discovered that SSSD incorrectly handled Group Policy Objects. When
SSSD is configured with too strict permissions causing the GPO to not be
readable, SSSD will allow all authenticated users to login instead of being
denied, contrary to expectations. This issue only affected Ubuntu 18.04
LTS. (CVE-2018-16838)

It was discovered that SSSD incorrectly handled users with no home
directory set. When no home directory was set, SSSD would return the root
directory instead of an empty string, possibly bypassing security measures.
This issue only affected Ubuntu 18.04 LTS. (CVE-2019-3811)

Cedric Buissart discovered that SSSD incorrectly handled the sssctl
command. In certain environments, a local user could use this issue to
execute arbitrary commands and possibly escalate privileges.
(CVE-2021-3621)

Update instructions:

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

Ubuntu 21.04:
sssd 2.4.0-1ubuntu6.1

Ubuntu 20.04 LTS:
sssd 2.2.3-3ubuntu0.7

Ubuntu 18.04 LTS:
sssd 1.16.1-1ubuntu1.8

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

References:
  https://ubuntu.com/security/notices/USN-5067-1
CVE-2018-10852, CVE-2018-16838, CVE-2019-3811, CVE-2021-3621

Package Information:
  https://launchpad.net/ubuntu/+source/sssd/2.4.0-1ubuntu6.1
  https://launchpad.net/ubuntu/+source/sssd/2.2.3-3ubuntu0.7
  https://launchpad.net/ubuntu/+source/sssd/1.16.1-1ubuntu1.8