GHSA-5hm8-vh6r-2cjq

CodeIgniter Shield Vulnerable to SameSite Attackers Bypassing the CSRF Protection

### Impact This vulnerability may allow [SameSite Attackers](https://canitakeyoursubdomain.name/) to bypass the [CodeIgniter4 CSRF protection](https://codeigniter4.github.io/userguide/libraries/security.html) mechanism with CodeIgniter Shield. For this attack to succeed, the attacker must have direct (or indirect, e.g., XSS) control over a subdomain site (e.g., `https://a.example.com/`) of the target site (e.g., `http://example.com/`). This vulnerability exists whether `Config\Security::$csrfProtection` is `'cookie'` or `'session'`. It is also exploitable whether `Config\Security::$regenerate` is `true` or `false`. ### Patches Upgrade to **CodeIgniter v4.2.3 or later** and **Shield v1.0.0-beta.2 or later**. ### Workarounds Do all of the following: - set `Config\Security::$csrfProtection` to `'session'` - remove old session data right after login (immediately after ID and password match) - regenerate CSRF token right after login (immediately after ID and password match) ### References - [CodeIgniter4 CSRF Protection](https://codeigniter4.github.io/userguide/libraries/security.html) - [SameSite Attacks](https://canitakeyoursubdomain.name/) - [SameSite Cookies](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Set-Cookie/SameSite) - [The great SameSite confusion](https://jub0bs.com/posts/2021-01-29-great-samesite-confusion/) ### For more information If you have any questions or comments about this advisory: * Open an issue or discussion in [codeigniter4/shield](https://github.com/codeigniter4/shield) * Email us at [security@codeigniter.com](mailto:security@codeigniter.com)