An issue was discovered in RubyGems 2.6 and later through 3.0.2. A crafted gem with a multi-line name is not handled correctly. Therefore, an attacker could inject arbitrary code to the stub line of gemspec, which is eval-ed by code in ensure_loadable_spec during the preinstall check.
https://lists.debian.org/debian-lts-announce/2020/08/msg00027.html
https://hackerone.com/reports/328571
https://access.redhat.com/errata/RHSA-2019:1972
http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00036.html