Devise is an authentication solution for Rails based on Warden. In versions 5.0.3 and below, when the Timeoutable module is enabled in Devise, the FailureApp#redirect_url method returns request.referrer — the HTTP Referer header, which is attacker-controllable — without validation for any non-GET request that results in a session timeout. An attacker who hosts a page with an auto-submitting cross-origin form can cause a victim with an expired Devise session to be redirected to an arbitrary external URL. This contrasts with the GET timeout path (which uses server-side attempted_path) and Devise's own store_location_for mechanism (which strips external hosts via extract_path_from_location), both of which are protected; only the non-GET timeout redirect path is unprotected. Expired-session users can be silently redirected from the trusted app domain to attacker-controlled URLs, enabling phishing and malware delivery while bypassing browser warnings. Note: Rails' built-in open-redirect protection does not mitigate this issue. Devise::FailureApp is an ActionController::Metal app with its own isolated copy of the relevant redirect configuration, so config.action_controller.action_on_open_redirect = :raise (and the older raise_on_open_redirects setting) do not reach it. This issue has been fixed in version 5.0.4.

Affected: RubyGems: devise

## Summary

When the `Timeoutable` module is enabled in Devise, the `FailureApp#redirect_url` method returns `request.referrer` — the HTTP `Referer` header, which is attacker-controllable — without validation for any non-GET request that results in a session timeout. An attacker who hosts a page with an auto-submitting cross-origin form can cause a victim with an expired Devise session to be redirected to an arbitrary external URL. This contrasts with the GET timeout path (which uses server-side `attempted_path`) and Devise's own `store_location_for` mechanism (which strips external hosts via `extract_path_from_location`), both of which are protected; only the non-GET timeout redirect path is unprotected.

## Details

The vulnerable code is in `lib/devise/failure_app.rb`:

```ruby def redirect_url if warden_message == :timeout flash[:timedout] = true if is_flashing_format?

path = if request.get? attempted_path # safe: server-side value from warden options else request.referrer # UNSAFE: HTTP Referer header, attacker-controlled end

path || scope_url else scope_url end end ```

This is passed directly to `redirect_to`:

```ruby def redirect store_location! # ... redirect_to redirect_url # redirect_url may be an external attacker URL end ```

The GET timeout path uses `attempted_path`, which is set server-side by Warden and cannot be influenced by the client. The `store_location!` method also only runs for GET…

Affected: Ubuntu:16.04:LTS: ruby-devise, Ubuntu:18.04:LTS: ruby-devise, Ubuntu:20.04:LTS: ruby-devise, Ubuntu:22.04:LTS: ruby-devise, Ubuntu:24.04:LTS: ruby-devise

Devise is an authentication solution for Rails based on Warden. In versions 5.0.3 and below, when the Timeoutable module is enabled in Devise, the FailureApp#redirect_url method returns request.referrer — the HTTP Referer header, which is attacker-controllable — without validation for any non-GET request that results in a session timeout. An attacker who hosts a page with an auto-submitting cross-origin form can cause a victim with an expired Devise session to be redirected to an arbitrary external URL. This contrasts with the GET timeout path (which uses server-side attempted_path) and Devise's own store_location_for mechanism (which strips external hosts via extract_path_from_location), both of which are protected; only the non-GET timeout redirect path is unprotected. Expired-session users can be silently redirected from the trusted app domain to attacker-controlled URLs, enabling phishing and malware delivery while bypassing browser warnings. Note: Rails' built-in open-redirect protection does not mitigate this issue. Devise::FailureApp is an ActionController::Metal app with its own isolated copy of the relevant redirect configuration, so config.action_controller.action_on_open_redirect = :raise (and the older raise_on_open_redirects setting) do not reach it. This issue has been fixed in version 5.0.4.