Unsafe cookie serialization strategy detected.

• Rule ID: ruby_rails_unsafe_cookie_serialization_strategy
• Languages: ruby
• Source: unsafe_cookie_serialization_strategy.yml

Description

JSON is the safest serialization strategy for untrusted data, such as cookie data, to avoid malicious code injection. By default, Rails uses JSON to serialize cookie values.

Remediations

❌ Avoid overriding the default cookie serializer

Rails.application.config.action_dispatch.cookies_serializer = :marshal

❌ Use the hybrid (Marshal and JSON) serializer option as a temporary solution only, for example when migrating from Marshal to JSON.

Rails.application.config.action_dispatch.cookies_serializer = :hybrid

Resources

• OWASP Rails Goat on Marshal and Remote Code Execution

Associated CWE

• CWE-94: Improper Control of Generation of Code ('Code Injection')

OWASP Top 10

• A03:2021 - Injection