Bundler provides a consistent environment for Ruby projects by tracking and installing the exact gems and versions that are needed.
Bundler, allows the installation of gems from different sources with the same names, when multiple top-level gem sources are used.
Remote attackers could inject arbitrary code via the gem install process.
There is no known workaround at this time.
All Bundler users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=dev-ruby/bundler-1.7.3"