There is a File Content Disclosure vulnerability in Action View <5.2.2.1, <5.1.6.2, <5.0.7.2, <4.2.11.1 and v3 where specially crafted accept headers can cause contents of arbitrary files on the target system's filesystem to be exposed.
https://www.exploit-db.com/exploits/46585/
https://weblog.rubyonrails.org/2019/3/13/Rails-4-2-5-1-5-1-6-2-have-been-released/
https://lists.debian.org/debian-lts-announce/2019/03/msg00042.html
https://groups.google.com/forum/#%21topic/rubyonrails-security/pFRKI96Sm8Q
https://access.redhat.com/errata/RHSA-2019:1289
https://access.redhat.com/errata/RHSA-2019:1149
https://access.redhat.com/errata/RHSA-2019:1147
https://access.redhat.com/errata/RHSA-2019:0796
http://www.openwall.com/lists/oss-security/2019/03/22/1
http://packetstormsecurity.com/files/152178/Rails-5.2.1-Arbitrary-File-Content-Disclosure.html
http://lists.opensuse.org/opensuse-security-announce/2019-05/msg00011.html