This problem was uncovered while testing with experimental DNS record types. It is possible to add records to BIND with null (zero length) rdata fields.
Processing of these records may lead to unexpected outcomes. Recursive servers may crash or disclose some portion of memory to the client. Secondary servers may crash on restart after transferring a zone containing these records. Master servers may corrupt zone data if the zone option "auto-dnssec" is set to "maintain". Other unexpected problems that are not listed here may also be encountered.
According to ISC's security advisory: This issue primarily affects recursive nameservers. Authoritative nameservers will only be impacted if an administrator configures experimental record types with no data. If the server is configured this way, then secondaries can crash on restart after transferring that zone. Zone data on the master can become corrupted if the zone with those records has named configured to manage the DNSSEC key rotation.
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Users who obtain BIND from a third-party vendor, such as their operating system vendor, should see the vendor information portion of this document for a partial list of affected vendors.
This vulnerability is addressed in ISC BIND versions 9.6-ESV-R7-P1, 9.7.6-P1, 9.8.3-P1, or 9.9.1-P1. Users of BIND from the original source distribution should upgrade to this version.