RubyGems version Ruby 2.2 series: 2.2.9 and earlier, Ruby 2.3 series: 2.3.6 and earlier, Ruby 2.4 series: 2.4.3 and earlier, Ruby 2.5 series: 2.5.0 and earlier, prior to trunk revision 62422 contains a Directory Traversal vulnerability in install_location function of package.rb that can result in path traversal when writing to a symlinked basedir outside of the root. This vulnerability appears to have been fixed in 2.7.6.
blog.rubygems.org/2018/02/15/2.7.6-released.html
lists.opensuse.org/opensuse-security-announce/2019-07/msg00036.html
access.redhat.com/errata/RHSA-2018:3729
access.redhat.com/errata/RHSA-2018:3730
access.redhat.com/errata/RHSA-2018:3731
access.redhat.com/errata/RHSA-2019:2028
access.redhat.com/errata/RHSA-2020:0542
access.redhat.com/errata/RHSA-2020:0591
access.redhat.com/errata/RHSA-2020:0663
github.com/rubygems/rubygems/commit/1b931fc03b819b9a0214be3eaca844ef534175e2
lists.debian.org/debian-lts-announce/2018/08/msg00028.html
usn.ubuntu.com/3621-1/
www.debian.org/security/2018/dsa-4219
www.debian.org/security/2018/dsa-4259