USN-3917-1: snapd vulnerability

21 March 2019

snapd vulnerability

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

  • Ubuntu 18.10
  • Ubuntu 18.04 LTS
  • Ubuntu 16.04 LTS
  • Ubuntu 14.04 LTS

Summary

An intended access restriction in snapd could be bypassed by strict mode snaps on 64 bit architectures.

Software Description

  • snapd - Daemon and tooling that enable snap packages

Details

The snapd default seccomp filter for strict mode snaps blocks the use of the ioctl() system call when used with TIOCSTI as the second argument to the system call. Jann Horn discovered that this restriction could be circumvented on 64 bit architectures. A malicious snap could exploit this to bypass intended access restrictions to insert characters into the terminal’s input queue. On Ubuntu, snapd typically will have already automatically refreshed itself to snapd 2.37.4 which is unaffected.

Update instructions

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

Ubuntu 18.10
snapd - 2.37.4+18.10.1
Ubuntu 18.04 LTS
snapd - 2.37.4+18.04.1
Ubuntu 16.04 LTS
snapd - 2.37.4ubuntu0.1
Ubuntu 14.04 LTS
snapd - 2.37.4~14.04.1

To update your system, please follow these instructions: https://wiki.ubuntu.com/Security/Upgrades.

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

References