A deserialization of untrusted data vulnernerability exists in rails < 5.2.4.3, rails < 6.0.3.1 that can allow an attacker to unmarshal user-provided objects in MemCacheStore and RedisCacheStore potentially resulting in an RCE.
https://www.debian.org/security/2020/dsa-4766
https://weblog.rubyonrails.org/2020/5/18/Rails-5-2-4-3-and-6-0-3-1-have-been-released/
https://lists.debian.org/debian-lts-announce/2020/07/msg00013.html
https://lists.debian.org/debian-lts-announce/2020/06/msg00022.html
https://hackerone.com/reports/413388
https://groups.google.com/g/rubyonrails-security/c/bv6fW4S0Y1c
http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00034.html
http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00031.html