==========================================================================
Ubuntu Security Notice USN-5142-2
December 06, 2021

samba regressions
==========================================================================

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

- Ubuntu 21.10
- Ubuntu 21.04
- Ubuntu 20.04 LTS

Summary:

USN-5142-1 introduced regressions in Samba.

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

Details:

USN-5142-1 fixed vulnerabilities in Samba. Some of the upstream changes
introduced regressions in name mapping and backups.

Please see the following upstream bugs for more information:
https://bugzilla.samba.org/show_bug.cgi?id=14901
https://bugzilla.samba.org/show_bug.cgi?id=14918

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:
  samba                           2:4.13.14+dfsg-0ubuntu0.21.10.3

Ubuntu 21.04:
  samba                           2:4.13.14+dfsg-0ubuntu0.21.04.3

Ubuntu 20.04 LTS:
  samba                           2:4.13.14+dfsg-0ubuntu0.20.04.3

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

References:
  https://ubuntu.com/security/notices/USN-5142-2
  https://ubuntu.com/security/notices/USN-5142-1
  https://launchpad.net/bugs/1950363, https://launchpad.net/bugs/1952187

Package Information:
  https://launchpad.net/ubuntu/+source/samba/2:4.13.14+dfsg-0ubuntu0.21.10.3
  https://launchpad.net/ubuntu/+source/samba/2:4.13.14+dfsg-0ubuntu0.21.04.3
  https://launchpad.net/ubuntu/+source/samba/2:4.13.14+dfsg-0ubuntu0.20.04.3