The remote host is missing an update to cyrus-imapd announced via advisory DSA 215-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20215-1

Timo Sirainen discovered a buffer overflow in the Cyrus IMAP server, which could be exploited by a remote attacker prior to logging in. A malicious user could craft a request to run commands on the server under the UID and GID of the cyrus server. For the current stable distribution (woody) this problem has been fixed in version 1.5.19-9.1. For the old stable distribution (potato) this problem has been fixed in version 1.5.19-2.2. For the current unstable distribution (sid) this problem has been fixed in version 1.5.19-9.10. The cyrus21-imapd packages are not vulnerable We recommend that you upgrade your cyrus-imapd package.