telnetd in Heimdal 0.6.x before 0.6.6 and 0.7.x before 0.7.2 allows remote unauthenticated attackers to cause a denial of service (server crash) via unknown vectors that trigger a null dereference.
https://exchange.xforce.ibmcloud.com/vulnerabilities/24763
http://www.vupen.com/english/advisories/2006/0653
http://www.vupen.com/english/advisories/2006/0628
http://www.vupen.com/english/advisories/2006/0456
http://www.ubuntu.com/usn/usn-253-1
http://www.stacken.kth.se/lists/heimdal-discuss/2006-02/msg00028.html
http://www.securityfocus.com/bid/16676
http://www.securityfocus.com/archive/1/426043/100/0/threaded
http://www.debian.org/security/2006/dsa-977
http://securityreason.com/securityalert/449
http://secunia.com/advisories/19005