checkpassword-reply in Dovecot before 2.2.7 performs setuid operations to a user who is authenticating, which allows local users to bypass authentication and…

checkpassword-reply in Dovecot before 2.2.7 performs setuid operations to a user who is authenticating, which allows local users to bypass authentication and access virtual email accounts by attaching to the process and using a restricted file descriptor to modify account information in the response to the dovecot-auth server.