CVE-2024-0227 (devise-two-factor): Devise-Two-Factor vulnerable to brute force attacks

Ruby Security Advisory

Devise-Two-Factor does not throttle or otherwise restrict login
attempts at the server by default. When combined with the Time-based
One Time Password algorithm’s (TOTP) inherent entropy limitations,
it’s possible for an attacker to bypass the 2FA mechanism through
brute-force attacks.

### Impact

If a user’s username and password have already been compromised an
attacker would be able to try possible TOTP codes and see if they
can hit a lucky collision to log in as that user. The user under
attack would not necessarily know that their account has been

### Patches

Devise-Two-Factor has not released any fixes for this vulnerability.
This library is open-ended by design and cannot solve this for all
applications natively. It’s recommended that any application leveraging
Devise-Two-Factor implement controls at the application level to
mitigate this threat. A non-exhaustive list of possible mitigations
can be found below.

#### Mitigations

1. Use the `lockable` strategy from Devise to lock a user after a
certain number of failed login attempts. See
for more information.

2. Configure a rate limit for your application, especially on the
endpoints used to log in. One such library to accomplish this is

3. When displaying authentication errors hide whether validating a
username/password combination failed or a two-factor code failed
behind a more generic error message.

### Acknowledgements

Christian Reitter ([Radically Open Security](
and Chris MacNaughton ([Centauri Solutions](