Buffer overflows in xtell (xtelld) 1.91.1 and earlier, and 2.x before 2.7, allows remote attackers to execute arbitrary code via (1) a long DNS hostname that is determined using reverse DNS lookups, (2) a long AUTH string, or (3) certain data in the xtell request.
http://www.securityfocus.com/bid/4193
http://www.iss.net/security_center/static/8312.php