=========================================================================Ubuntu Security Notice USN-4930-1
April 29, 2021

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

- Ubuntu 21.04
- Ubuntu 20.10
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

Samba would allow unintended access to files over the network.

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

Details:

Peter Eriksson discovered that Samba incorrectly handled certain negative
idmap cache entries. This issue could result in certain users gaining
unauthorized access to files, contrary to expected behaviour.

Update instructions:

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

Ubuntu 21.04:
  samba                           2:4.13.3+dfsg-1ubuntu2.1

Ubuntu 20.10:
  samba                           2:4.12.5+dfsg-3ubuntu4.3

Ubuntu 20.04 LTS:
  samba                           2:4.11.6+dfsg-0ubuntu1.8

Ubuntu 18.04 LTS:
  samba                           2:4.7.6+dfsg~ubuntu-0ubuntu2.23

Ubuntu 16.04 LTS:
  samba                           2:4.3.11+dfsg-0ubuntu0.16.04.34

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

References:
  https://ubuntu.com/security/notices/USN-4930-1
  CVE-2021-20254

Package Information:
  https://launchpad.net/ubuntu/+source/samba/2:4.13.3+dfsg-1ubuntu2.1
  https://launchpad.net/ubuntu/+source/samba/2:4.12.5+dfsg-3ubuntu4.3
  https://launchpad.net/ubuntu/+source/samba/2:4.11.6+dfsg-0ubuntu1.8
  https://launchpad.net/ubuntu/+source/samba/2:4.7.6+dfsg~ubuntu-0ubuntu2.23
  https://launchpad.net/ubuntu/+source/samba/2:4.3.11+dfsg-0ubuntu0.16.04.34