iterator.c in NLnet Labs Unbound before 1.5.1 does not limit delegation chaining, which allows remote attackers to cause a denial of service (memory and CPU consumption) via a large or infinite number of referrals.
http://cert.ssi.gouv.fr/site/CERTFR-2014-AVI-512/index.html
http://unbound.net/downloads/patch_cve_2014_8602.diff
http://www.debian.org/security/2014/dsa-3097
http://www.kb.cert.org/vuls/id/264212
http://www.oracle.com/technetwork/topics/security/linuxbulletinoct2015-2719645.html
http://www.securityfocus.com/bid/71589