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, and Ruby 2.5 series: 2.5.0 and earlier, prior to trunk revision 62422 contain an Improper Verification of Cryptographic Signature vulnerability in package.rb. This can result in a mis-signed gem being installed, as the tarball would contain multiple gem signatures. This vulnerability has 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/jruby/jruby/commit/0b06b48ab4432237ce5fc1bef47f2c6bcf7843f7
github.com/rubygems/rubygems
github.com/rubygems/rubygems/commit/f5042b879259b1f1ce95a0c5082622c646376693
lists.debian.org/debian-lts-announce/2018/04/msg00000.html
lists.debian.org/debian-lts-announce/2018/04/msg00001.html
lists.debian.org/debian-lts-announce/2018/04/msg00023.html
lists.debian.org/debian-lts-announce/2018/07/msg00012.html
lists.debian.org/debian-lts-announce/2019/05/msg00028.html
nvd.nist.gov/vuln/detail/CVE-2018-1000076
usn.ubuntu.com/3621-1
www.debian.org/security/2018/dsa-4219
www.debian.org/security/2018/dsa-4259