CVE-2026-32700: Devise has a confirmable "change email" race condition that permits user to confirm email they have no access to

Impact

A race condition in Devise's Confirmable module allows an attacker to confirm an email address they do not own. This affects any Devise application using the reconfirmable option (the default when using Confirmable with email changes).

By sending two concurrent email change requests, an attacker can desynchronize the confirmationtoken and unconfirmedemail fields. The confirmation token is sent to an email the attacker controls, but the unconfirmedemail in the database points to a victim's email address. When the attacker uses the token, the victim's email is confirmed on the attacker's account.

Patches

This is patched in Devise v5.0.3. Users should upgrade as soon as possible.

Workarounds

Applications can override this specific method from Devise models to force unconfirmedemail to be persisted when unchanged: (assuming your model is User)

ruby class User < ApplicationRecord protected

def postponeemailchangeuntilconfirmationandregenerateconfirmationtoken unconfirmedemailwillchange! super end end

Note: Mongoid does not seem to respect that willchange! should force the attribute to be persisted, even if it did not really change, so you might have to implement a workaround similar to Devise by setting changedattributes["unconfirmedemail"] = nil as well.