Puma is a Ruby/Rack web server built for parallelism. From 5.5.0 until 7.2.1 and 8.0.2, Puma is vulnerable to source IP spoofing when set_remote_address proxy_protocol: :v1 is enabled and persistent connections are used because Puma incorrectly re-parses PROXY protocol headers after each keep-alive request on the same connection, allowing an attacker to inject a second PROXY header and overwrite REMOTE_ADDR. This issue is fixed in versions 7.2.1 and 8.0.2.
Exploitability
AV:NAC:LPR:NUI:NScope
S:UImpact
C:NI:HA:NCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N