The compress_add_dlabel_points function in dns/Compress.c in MaraDNS 1.4.03, 1.4.05, and probably other versions allows remote attackers to cause a denial of service (segmentation fault) and possibly execute arbitrary code via a long DNS hostname with a large number of labels, which triggers a heap-based buffer overflow.
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=610834
http://secunia.com/advisories/43027
http://secunia.com/advisories/43107
http://www.debian.org/security/2011/dsa-2196
http://www.openwall.com/lists/oss-security/2011/01/24/1
http://www.openwall.com/lists/oss-security/2011/01/24/6
http://www.securityfocus.com/bid/45966