A possible escalation to RCE vulnerability exists when using YAML serialized columns in Active Record < 7.0.3.1, <6.1.6.1, <6.0.5.1 and <5.2.8.1 which could allow an attacker, that can manipulate data in the database (via means like SQL injection), the ability to escalate to an RCE.
Puma < 5.6.9 - Authorization Bypass via Underscore Header Clobbering
Puma is a Ruby/Rack web server built for parallelism. In affected versions clients could clobber values set by intermediate proxies (such as X-Forwarded-For) by providing a underscore version of the same header (X-Forwarded_For). Any users relying on proxy set variables is affected. v6.4.3/v5.6.9 now discards any headers using underscores if the non-underscore version also exists. Effectively, allowing the proxy defined headers to always win. Users are advised to upgrade. Nginx has a underscores_in_headers configuration variable to discard these headers at the proxy level as a mitigation. Any users that are implicitly trusting the proxy defined headers for security should immediately cease doing so until upgraded to the fixed versions.