Package Instance

Better Auth Has Two-Factor Authentication Bypass via Premature Session Caching (session.cookieCache)
### Summary

Under certain configurations, sessions may be considered valid before two-factor authentication (2FA) is fully completed. This can allow access to authenticated routes without verifying the second factor.

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### Description

When two-factor authentication is enabled, the authentication flow correctly identifies users who require additional verification and defers full authentication until the second factor is completed.

However, when `session.cookieCache` is enabled, the session generated during the initial sign-in step may be cached as valid **prior to 2FA verification**. Subsequent session lookups may then return this cached session without re-evaluating the 2FA requirement.

This results in a situation where session validity can be established before all authentication constraints are satisfied.

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### Impact

An attacker (or user) with valid primary credentials may gain access to protected application routes without completing the required second authentication factor.

Any application using `better-auth` with both two-factor authentication and session cookie caching enabled may be affected.

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### Mitigation

* Upgrade to a version of `better-auth` that includes the fix for this issue.
* Ensure that session caching does not treat sessions as fully authenticated until all required authentication steps, including 2FA, are completed.
* As a temporary workaround, disable `session.cookieCache` when using two-factor authentication.