PowerDNS Recursor before 3.1.5 uses insufficient randomness to calculate (1) TRXID values and (2) UDP source port numbers, which makes it easier for remote attackers to poison a DNS cache, related to (a) algorithmic deficiencies in rand and random functions in external libraries, (b) use of a 32-bit seed value, and (c) choice of the time of day as the sole seeding information.

PowerDNS Recursor 3.1.3 and earlier allows remote attackers to cause a denial of service (resource exhaustion and application crash) via a CNAME record with a zero TTL, which triggers an infinite loop.

Buffer overflow in PowerDNS Recursor 3.1.3 and earlier might allow remote attackers to execute arbitrary code via a malformed TCP DNS query that prevents Recursor from properly calculating the TCP DNS query length.

The recursor in PowerDNS before 3.0.1 allows remote attackers to cause a denial of service (application crash) via malformed EDNS0 packets.

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.