The remote host is missing an update to mutt announced via advisory DSA 096-1.
Joost Pol found a buffer overflow in the address handling code of mutt (a popular mail user agent). Even though this is a one byte overflow this is exploitable. This has been fixed upstream in version 18.104.22.168 and 1.3.25. The relevant patch has been added to version 1.2.5-5 of the Debian package.