If certain directories exist in a director that is managed by
`Rack::Directory`, an attacker could, using this vulnerability,
read the contents of files on the server that were outside of
the root specified in the Rack::Directory initializer.
For Debian 8 "Jessie", this problem has been fixed in version
We recommend that you upgrade your ruby-rack packages.
Further information about Debian LTS security advisories, how to apply
these updates to your system and frequently asked questions can be
found at: https://wiki.debian.org/LTS