Untrusted users can run pending migrations in production in Rails

There is a vulnerability in versions of Rails prior to 6.0.3.2 that allowed an untrusted user to run any pending migrations on a Rails app running in production.

This vulnerability has been assigned the CVE identifier CVE-2020-8185.

Versions Affected: 6.0.0 < rails < 6.0.3.2
Not affected: Applications with config.action_dispatch.show_exceptions = false (this is not a default setting in production)
Fixed Versions: rails >= 6.0.3.2

Impact

Using this issue, an attacker would be able to execute any migrations that are pending for a Rails app running in production mode. It is important to note that an attacker is limited to running migrations the application developer has already defined in their application and ones that have not already run.

Workarounds

Until such time as the patch can be applied, application developers should disable the ActionDispatch middleware in their production environment via a line such as this one in their config/environment/production.rb:

config.middleware.delete ActionDispatch::ActionableExceptions