[USN-4424-1] snapd vulnerabilities

Emilia Torino emilia.torino at canonical.com
Wed Jul 15 18:20:08 UTC 2020

Ubuntu Security Notice USN-4424-1
July 15, 2020

snapd vulnerabilities

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

- Ubuntu 20.04 LTS
- Ubuntu 19.10
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS


An intended access restriction in snapd could be bypassed by strict mode

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


It was discovered that cloud-init as managed by snapd on Ubuntu Core 16
and Ubuntu Core 18 devices ran on every boot without restrictions. A
physical attacker could exploit this to craft cloud-init
user-data/meta-data via external media to perform arbitrary changes on
the device to bypass intended security mechanisms such as full disk
encryption. This issue did not affect traditional Ubuntu systems.

It was discovered that snapctl user-open allowed altering the
XDG_DATA_DIRS environment variable when calling the system xdg-open. A
malicious snap could exploit this to bypass intended access restrictions
to control how the host system xdg-open script opens the URL. This issue
did not affect Ubuntu Core systems. (CVE-2020-11934)

Update instructions:

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

Ubuntu 20.04 LTS:
  snapd                           2.45.1+20.04.2

Ubuntu 19.10:
  snapd                           2.45.1+19.10.2

Ubuntu 18.04 LTS:
  snapd                           2.45.1+18.04.2

Ubuntu 16.04 LTS:
  snapd                           2.45.1ubuntu0.2

In general, a standard system update will make all the necessary changes.
On Ubuntu, snapd will automatically refresh itself to snapd 2.45.2 which
is unaffected.

  CVE-2020-11933, CVE-2020-11934

Package Information:

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