Nokogiri gem, via libxml, is affected by DoS vulnerabilities

The version of libxml2 packaged with Nokogiri contains a
vulnerability. Nokogiri has mitigated these issue by upgrading to
libxml 2.9.6.

It was discovered that libxml2 incorrecty handled certain files. An attacker
could use this issue with specially constructed XML data to cause libxml2 to
consume resources, leading to a denial of service.