An issue has been found in PowerDNS Recursor allowing a remote user to craft a DNS query that will cause an answer without DNSSEC records to be inserted into the packet cache and be returned to clients asking for DNSSEC records, thus hiding the presence of DNSSEC signatures for a specific qname and qtype. For a DNSSEC-signed domain, this means that clients performing DNSSEC validation by themselves might consider the answer to be bogus until it expires from the packet cache, leading to a denial of service.
This issue has been assigned CVE-2018-14626.
PowerDNS Recursor from 4.0.0 up to and including 4.1.4 is affected.
We would like to thank Kees Monshouwer for finding and subsequently reporting this issue.