bind: failure to clear existing RRSIG records when a NO DATA is negatively cached could DoS named

named in ISC BIND 9.6.2 before 9.6.2-P3, 9.6-ESV before 9.6-ESV-R3, and 9.7.x before 9.7.2-P3 does not properly handle the combination of signed negative responses and corresponding RRSIG records in the cache, which allows remote attackers to cause a denial of service daemon crash via a query for...