The remote host is vulnerable to a buffer overflow.
According to its banner, the remote Cyrus IMAPD server is vulnerable to multiple remote buffer overflow attacks. An attacker exploiting these flaws would need to be able to communicate with the IMAPD server (usually on TCP port 143). A successful attack would result in the attacker executing arbitrary code on the IMAPD server.
Upgrade to version 2.2.12 or higher.