Unbound before 1.3.4 does not properly verify signatures for NSEC3 records, which allows remote attackers to cause secure delegations to be downgraded via DNS spoofing or other DNS-related attacks in conjunction with crafted delegation responses.
https://exchange.xforce.ibmcloud.com/vulnerabilities/53729
http://www.vupen.com/english/advisories/2009/2875
http://www.openwall.com/lists/oss-security/2009/10/09/3
http://www.openwall.com/lists/oss-security/2009/10/09/2
http://www.debian.org/security/2009/dsa-1963
http://unbound.net/pipermail/unbound-users/2009-October/000852.html
http://secunia.com/advisories/37913