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Ubuntu Security Notice USN-5292-3
February 18, 2022

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

- Ubuntu 16.04 ESM
- Ubuntu 14.04 ESM

Summary:

Several security issues were fixed in snapd.

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

Details:

USN-5292-1 fixed several vulnerabilities in snapd. This update provides the
corresponding update for Ubuntu 14.04 ESM and Ubuntu 16.04 ESM.

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 16.04 ESM:
  snap-confine                    2.54.3+16.04~esm2
  snapd                           2.54.3+16.04~esm2

Ubuntu 14.04 ESM:
  snap-confine                    2.54.3+14.04~esm1
  snapd                           2.54.3+14.04~esm1

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

References:
  https://ubuntu.com/security/notices/USN-5292-3
  https://ubuntu.com/security/notices/USN-5292-1
  CVE-2021-3155, CVE-2021-4120, CVE-2021-44730, CVE-2021-44731