USN-3917-1: snapd vulnerability

21 March 2019

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



  • snapd - Daemon and tooling that enable snap packages


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
Ubuntu 18.04
Ubuntu 16.04
Ubuntu 14.04

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