⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● Medium · CVSS 6.1

How to Fix CVE-2026-40295: Open Redirect in devise

Other vulnerabilities in the same area that are worth patching alongside this one:

*By Sai Kiran Pandrala*

⚡ At a glance
SeverityCVSS 6.1 - Medium
Actively exploited?Not currently listed in CISA KEV
Affected< 5.0.4
Fixed inversion
Type (CWE)CWE-601: URL Redirection to Untrusted Site ('Open Redirect')

What is CVE-2026-40295?

CVE-2026-40295 is an open-redirect flaw in devise. The product forwards users to a URL taken from a parameter without validating the destination, which phishing campaigns use to abuse the product's trusted domain. Vendor 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.

Why this CVE matters

Open redirects on a trusted domain are routinely used by phishing kits to land victims on credential-harvesting pages while bouncing through a domain the victim trusts.

For deployments of devise that have been exposed to the public internet during the disclosure window, the operating assumption should be that scanning has already happened. Even where exploitation has not been publicly observed, scanning for the vulnerable fingerprint is cheap and routine. Patching closes the door; log review and credential rotation close out the rest of the response.

Am I affected?

You are affected if your installation matches any of these version ranges:

Check your installed version against the list above. If you cannot determine the version, treat the system as affected and follow the upgrade path below.

Open devise's About dialog or run the vendor-documented version-check command. Compare the result against the affected ranges in the advisory.

How to fix CVE-2026-40295

  1. Read the vendor advisory in full: https://github.com/heartcombo/devise/security/advisories/GHSA-jp94-3292-c3xv
  2. Upgrade devise to the patched build listed in the vendor advisory.
  3. Back up the configuration (and database, where applicable) before upgrading.
  4. Apply the patch in a maintenance window. For HA pairs, upgrade the standby node first, fail over, then upgrade the former primary.
  5. Restart the affected service so the patched binary loads, then verify the new version (see verification section).

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Update the Ruby gem devise to 5.0.4

Vendor advisory: https://github.com/heartcombo/devise/security/advisories/GHSA-jp94-3292-c3xv


# Update a single gem.
bundle update devise

# Or pin in Gemfile then re-resolve.
sed -i "s/^gem 'devise'.*$/gem 'devise', '~> 5.0.4'/" Gemfile
bundle install

# Verify the resolved version.
bundle info devise


# Same flow on Windows.
bundle update devise
bundle info devise

Verify the fix landed


# Vendor advisory: https://github.com/heartcombo/devise/security/advisories/GHSA-jp94-3292-c3xv
# 1. Confirm the running version matches the fixed-in version listed above.

# 2. Re-scan with your vulnerability scanner (Nessus, Qualys, Tenable, OpenVAS).
#    The scanner should no longer flag this CVE on the patched target.

# 3. Inspect recent service / kernel logs for crash-loops or rollback events.
journalctl -u <service> --since "10 minutes ago"
dmesg --since "10 minutes ago"

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If you cannot patch immediately

Block the redirect parameter at a reverse proxy, or strip it from inbound requests. Patch as the durable fix.

How to verify the fix worked

If your installation was internet-reachable during the disclosure window, treat log review as part of the remediation rather than an optional follow-up. Look for log entries that do not match your normal request patterns, especially repeated requests to the same uncommon endpoint, and any administrative changes you cannot tie back to a known operator.

Frequently asked questions

Is CVE-2026-40295 being exploited in the wild?

Public exploitation has not been confirmed by CISA at the time of writing. Treat the patch as time-sensitive anyway; reports often lag actual abuse.

Will a WAF or IDS rule fully mitigate CVE-2026-40295?

No. Network-layer filters can reduce noise and slow opportunistic scanners, but they will not stop a determined attacker. The vendor patch is the only durable fix.

How long should I plan for the upgrade?

Typical vendor-documented upgrade windows for devise run from a few minutes to under an hour depending on cluster size. Test in a staging environment first and follow the vendor's documented HA upgrade order.

References

*This guide was assembled from the official vendor advisory, the NVD record, and the CISA KEV catalog entry on 2026-05-25. Always confirm against the vendor advisory before applying changes in production.*