The remote host is vulnerable to a 'format string' vulnerability
The remote host is running a version of the Mutt email client that contains a format string vulnerability. Due to improper handling of input from IMAP servers, it may be possible for a malicious IMAP server to send a specially crafted message to the mutt client that will cause execution of arbitrary code in the context of the mutt user.
Upgrade to either 1.4.1 or 1.5. Patches/upgrades are available at www.mutt.org