USN-1238-1: Puppet vulnerability

24 October 2011

puppet vulnerability

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

  • Ubuntu 11.10
  • Ubuntu 11.04
  • Ubuntu 10.10
  • Ubuntu 10.04 LTS


The Puppet master server could be impersonated in certain configurations.

Software Description

  • puppet - Centralized configuration management


It was discovered that Puppet incorrectly handled the non-default “certdnsnames” option when generating certificates. If this setting was added to puppet.conf, the puppet master’s DNS alt names were added to the X.509 Subject Alternative Name field of all certificates, not just the puppet master’s certificate. An attacker that has an incorrect agent certificate in his possession can use it to impersonate the puppet master in a man-in-the-middle attack.

Update instructions

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

Ubuntu 11.10
puppet-common - 2.7.1-1ubuntu3.2
Ubuntu 11.04
puppet-common - 2.6.4-2ubuntu2.5
Ubuntu 10.10
puppet-common - 2.6.1-0ubuntu2.4
Ubuntu 10.04 LTS
puppet-common - 0.25.4-2ubuntu6.5

To update your system, please follow these instructions:

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

If your puppet master’s puppet.conf file has ever contained the “certdnsnames” setting, you must reissue your site certificates, or apply another mitigation technique. Please see the upstream advisory for more information: