An attacker can publish a zone containing specific Resource Record Sets. Processing and caching results for these sets can lead to an illegal memory accesses and crash of the Recursor, causing a denial of service.
CVSS Score: 7.5, see https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H&version=3.1
The remedy is: upgrade to the patched 5.2.1 version.
We would like to thank Volodymyr Ilyin for bringing this issue to our attention.