CORS for Ruby on Rails
medium4 checks
CORS decides which origins may read your API responses. A wildcard turns an authenticated API into a public one.
What Ruby on Rails must have
- Access-Control-Allow-Origin limited to known origins
- No wildcard combined with credentials
- No reflection of arbitrary Origin headers
- Preflight responses only allow the methods actually used
How to fix it
- 1Replace wildcards with an explicit allowlist
- 2Validate Origin before echoing it and reject unknown origins early
Ruby on Rails context
Ruby MVC framework with convention-over-configuration defaults.
Keep Rails patched (several critical deserialisation CVEs) and never expose /rails/info in production.