Hash#slice in lib/i18n/core_ext/hash.rb in the i18n gem before 0.8.0 for Ruby allows remote attackers to cause a denial of service (application crash) via a call in a situation where :some_key is present in keep_keys but not present in the hash.
https://lists.debian.org/debian-lts-announce/2018/11/msg00021.html
https://github.com/svenfuchs/i18n/releases/tag/v0.8.0