Ruby on Rails CookieStore session cookie persistence

Description

Ruby on Rails applications using the default CookieStore session mechanism store session data entirely in client-side cookies without maintaining server-side session records. This design limitation prevents the server from truly invalidating sessions when users log out or when sessions are explicitly terminated. As a result, session cookies remain valid indefinitely until their expiration time, even after logout, allowing them to be replayed to regain authenticated access.

Remediation

Migrate from CookieStore to a server-side session storage mechanism that allows proper session invalidation. Implement one of the following solutions:

Option 1: Use ActiveRecord session store
Generate the session migration and configure Rails to use database-backed sessions:

rails generate session_migration
rake db:migrate

Then update config/initializers/session_store.rb:

YourApp::Application.config.session_store :active_record_store

Option 2: Use Redis or Memcached session store
Add the appropriate gem and configure session storage to use a centralized cache that supports expiration and deletion.

Additional hardening:
- Implement explicit session invalidation on logout by clearing server-side session records
- Set short session expiration times appropriate to your application's security requirements
- Rotate session identifiers after authentication and privilege changes
- Use secure cookie flags (HttpOnly, Secure, SameSite) to reduce cookie theft risk