The twofactorgauthenticator plugin for Roundcube is vulnerable to brute-forcing of the second-factor code. Due to the lack of rate limiting, an attacker who obtains user's password can submit arbitrary 6-digit codes, resulting in second-factor bypass and unauthorized access to the system. This issue was fixed in commit 4640889.

The twofactorgauthenticator plugin for Roundcube is vulnerable to session persistence after failed 2FA verification. Due to the lack of server-side session destruction, an attacker can ignore the logout redirect and keep the session alive. This may allow an attacker who obtains user's password to e.g. brute force the second-factor code. This issue was fixed in commit 4640889.

The twofactorgauthenticator plugin for Roundcube is vulnerable to 2fa authentication bypass by spoofed client address headers. Due to the lack of validation of the Client-IP and X-Forwarded-For headers, an attacker who obtains user's password can spoof a whitelisted IP address, resulting in the second factor being bypassed. This issue was fixed in commit 4640889.