USN-3395-1: c-ares vulnerability

Ubuntu Security Notice USN-3395-1

17th August, 2017

c-ares vulnerability

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

  • Ubuntu 17.04
  • Ubuntu 16.04 LTS
  • Ubuntu 14.04 LTS


c-ares could be made to crash if it received specially crafted network traffic.

Software description

  • c-ares - library for asynchronous name resolution


It was discovered that c-ares incorrectly handled certain NAPTR responses.
A remote attacker could possibly use this issue to cause applications using
c-ares to crash, resulting in a denial of service.

Update instructions

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

Ubuntu 17.04:
libc-ares2 1.12.0-1ubuntu0.1
Ubuntu 16.04 LTS:
libc-ares2 1.10.0-3ubuntu0.2
Ubuntu 14.04 LTS:
libc-ares2 1.10.0-2ubuntu0.2

To update your system, please follow these instructions:

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