The remote host is vulnerable to a buffer overflow.
The remote host is running Citadel/UX, a BBS software for Unix systems. There is a format string issue in the remote version of this software that may be exploited by an attacker to execute arbitrary commands on the remote host. The remote version of Citadel/UX is also known to be vulnerable to a buffer overflow in the way that select() function is performed.
Upgrade or patch according to vendor recommendations.