CVE-2021-25214

Incremental zone transfers (IXFR) provide a way of transferring changed portion(s) of a zone between servers. An IXFR stream containing SOA records with an owner name other than the transferred zone's apex may cause the receiving named server to inadvertently remove the SOA record for the zone in question from the zone database. This leads to an assertion failure when the next SOA refresh query for that zone is made.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Disabling incremental zone transfers (IXFR) by setting "request-ixfr no;" in the desired configuration block (options, zone, or server) prevents the failing assertion from being evaluated.