[USN-5292-4] snapd regression

[Paulo Flabiano Smorigo]

==========================================================================
Ubuntu Security Notice USN-5292-4
February 24, 2022

snapd regression
==========================================================================

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

- Ubuntu 21.10
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 ESM
- Ubuntu 14.04 ESM

Summary:

USN-5292-1 introduced a regression in snapd.

Software Description:
- snapd: Daemon and tooling that enable snap packages

Details:

USN-5292-1 fixed a vulnerability in snapd. Unfortunately that update introduced
a regression that could break the fish shell. This update fixes the problem.

We apologize for the inconvenience.

Original advisory details:

 James Troup discovered that snap did not properly manage the permissions for
 the snap directories. A local attacker could possibly use this issue to expose
 sensitive information. (CVE-2021-3155)
 
 Ian Johnson discovered that snapd did not properly validate content interfaces
 and layout paths. A local attacker could possibly use this issue to inject
 arbitrary AppArmor policy rules, resulting in a bypass of intended access
 restrictions. (CVE-2021-4120)
 
 The Qualys Research Team discovered that snapd did not properly validate the
 location of the snap-confine binary. A local attacker could possibly use this
 issue to execute other arbitrary binaries and escalate privileges.
 (CVE-2021-44730)
 
 The Qualys Research Team discovered that a race condition existed in the snapd
 snap-confine binary when preparing a private mount namespace for a snap. A
 local attacker could possibly use this issue to escalate privileges and
 execute arbitrary code. (CVE-2021-44731)

Update instructions:

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

Ubuntu 21.10:
  snap-confine                    2.54.3+21.10.1ubuntu0.2
  snapd                           2.54.3+21.10.1ubuntu0.2

Ubuntu 20.04 LTS:
  snap-confine                    2.54.3+20.04.1ubuntu0.2
  snapd                           2.54.3+20.04.1ubuntu0.2

Ubuntu 18.04 LTS:
  snap-confine                    2.54.3+18.04.2ubuntu0.2
  snapd                           2.54.3+18.04.2ubuntu0.2

Ubuntu 16.04 ESM:
  snap-confine                    2.54.3+16.04.0ubuntu0.1~esm4
  snapd                           2.54.3+16.04.0ubuntu0.1~esm4

Ubuntu 14.04 ESM:
  snap-confine                    2.54.3+14.04.0ubuntu0.1~esm3
  snapd                           2.54.3+14.04.0ubuntu0.1~esm3

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

References:
  https://ubuntu.com/security/notices/USN-5292-4
  https://ubuntu.com/security/notices/USN-5292-1
  https://bugs.launchpad.net/ubuntu/+source/snapd/+bug/1961365, https://bugs.launchpad.net/ubuntu/+source/snapd/+bug/1961791

Package Information:
  https://launchpad.net/ubuntu/+source/snapd/2.54.3+21.10.1ubuntu0.2
  https://launchpad.net/ubuntu/+source/snapd/2.54.3+20.04.1ubuntu0.2
  https://launchpad.net/ubuntu/+source/snapd/2.54.3+18.04.2ubuntu0.2
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