In s/qmail through 4.0.07, an active MitM can inject arbitrary plaintext commands into a STARTTLS encrypted session between an SMTP client …

In s/qmail through 4.0.07, an active MitM can inject arbitrary plaintext commands into a STARTTLS encrypted session between an SMTP client and s/qmail. This allows e-mail messages and user credentials to be sent to the MitM attacker.