CoreDNS is a DNS server written in Go. From 1.9.4 until 1.14.5, a network DNS client allowed to request AXFR for a CoreDNS zone can trigger a panic when CoreDNS is configured with k8s_external headless-service zone transfers and Kubernetes contains a headless service endpoint with no declared ports; plugin/kubernetes/object/endpoint.go creates Port: -1, plugin/k8s_external/msg_to_dns.go skips that service, plugin/k8s_external/transfer.go sends an empty []dns.RR batch, and plugin/transfer/transfer.go indexes records[0] without checking the batch is non-empty. This issue is fixed in version 1.14.5.
https://github.com/coredns/coredns/security/advisories/GHSA-74w3-63xv-x9mv
https://github.com/coredns/coredns/releases/tag/v1.14.5
https://github.com/coredns/coredns/pull/8207
https://github.com/coredns/coredns/commit/ab318db7b4a3a19273852ed627f54888198c8efb