RubyGems version 2.6.12 and earlier is vulnerable to a DNS hijacking vulnerability that allows a MITM attacker to force the RubyGems client to download and install gems from a server that the attacker controls.
Exploitability
AV:NAC:HPR:NUI:NScope
S:UImpact
C:HI:HA:H8.1/CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:HOther