RubyGems is vulnerable to remote code execution attacks. YAML deserialization of gem specifications can bypass class white lists. A remote, unauthenticated attacker could create specially crafted, serialized objects to be possibly used for remote code execution.
blog.rubygems.org/2017/10/09/2.6.14-released.html
blog.rubygems.org/2017/10/09/unsafe-object-deserialization-vulnerability.html
www.securityfocus.com/bid/101275
access.redhat.com/errata/RHSA-2017:3485
access.redhat.com/errata/RHSA-2018:0378
access.redhat.com/errata/RHSA-2018:0583
access.redhat.com/errata/RHSA-2018:0585
access.redhat.com/security/updates/classification/#moderate
bugzilla.redhat.com/show_bug.cgi?id=1506785
github.com/rubygems/rubygems/commit/510b1638ac9bba3ceb7a5d73135dafff9e5bab49
hackerone.com/reports/274990
lists.debian.org/debian-lts-announce/2018/07/msg00012.html
usn.ubuntu.com/3553-1/
usn.ubuntu.com/3685-1/
www.debian.org/security/2017/dsa-4031