bind: key algorithm rollover may mark secure answers as insecure

named in ISC BIND 9.x before 9.6.2-P3, 9.7.x before 9.7.2-P3, 9.4-ESV before 9.4-ESV-R4, and 9.6-ESV before 9.6-ESV-R3 does not properly determine the security status of an NS RRset during a DNSKEY algorithm rollover, which might allow remote attackers to cause a denial of service DNSSEC validati...