USN-3673-1: Unbound vulnerability

7 June 2018

unbound vulnerability

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

  • Ubuntu 18.04 LTS
  • Ubuntu 17.10
  • Ubuntu 16.04 LTS
  • Ubuntu 14.04 LTS


A security issue was fixed in Unbound.

Software Description

  • unbound - validating, recursive, caching DNS resolver


Ralph Dolmans and Karst Koymans discovered that Unbound did not properly handle certain NSEC records. An attacker could use this to to prove the non-existence (NXDOMAIN answer) of an existing wildcard record, or trick Unbound into accepting a NODATA proof.

Update instructions

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

Ubuntu 18.04 LTS
libunbound2 - 1.6.7-1ubuntu2.1
unbound - 1.6.7-1ubuntu2.1
Ubuntu 17.10
libunbound2 - 1.6.5-1ubuntu0.2
unbound - 1.6.5-1ubuntu0.2
Ubuntu 16.04 LTS
libunbound2 - 1.5.8-1ubuntu1.1
unbound - 1.5.8-1ubuntu1.1
Ubuntu 14.04 LTS
libunbound2 - 1.4.22-1ubuntu4.14.04.3
unbound - 1.4.22-1ubuntu4.14.04.3

To update your system, please follow these instructions:

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