bind: denial of service

A very uncommon combination of zone data has been found that triggers a
bug in BIND, with the result that named will exit with a "REQUIRE"
failure in name.c when validating the data returned in answer to a
recursive query.

This means that a recursive resolver that is performing DNSSEC
validation can be deliberately stopped by an attacker who can cause the
resolver to perform a query against a maliciously-constructed zone.