An issue was discovered in PowerDNS Authoritative through 4.3.0 when --enable-experimental-gss-tsig is used. A remote, unauthenticated attacker might be able to cause a double-free, leading to a crash or possibly arbitrary code execution. by sending crafted queries with a GSS-TSIG signature.
https://doc.powerdns.com/authoritative/security-advisories/powerdns-advisory-2020-06.html