PowerDNS before 2.9.21.2 allows remote attackers to cause a denial of service (daemon crash) via a CH HINFO query.

The DNS implementation of PowerDNS 2.9.16 and earlier allows remote attackers to cause a denial of service via a compressed DNS packet with a label length byte with an incorrect offset, which could trigger an infinite loop.

PowerDNS before 2.9.18, when allowing recursion to a restricted range of IP addresses, does not properly handle questions from clients that are denied recursion, which could cause a "blank out" of answers to those clients that are allowed to use recursion.

PowerDNS before 2.9.18, when running with an LDAP backend, does not properly escape LDAP queries, which allows remote attackers to cause a denial of service (failure to answer ldap questions) and possibly conduct an LDAP injection attack.

The DNSPacket::expand method in dnspacket.cc in PowerDNS before 2.9.17 allows remote attackers to cause a denial of service by sending a random stream of bytes.