CVE-2026-86003

CVE-2026-86003 · CoreDNS DoH/DoQ/gRPC bypass UPDATE rejection enforced on UDP/TCP

This page contains facts from public vulnerability sources. Check the original advisory before updating.

CoreDNS is a DNS server written in Go. Prior to 1.14.7, the DNS-over-HTTPS, DNS-over-HTTP/3, DNS-over-QUIC, and DNS-over-gRPC listeners in plugin/pkg/doh/doh.go, core/dnsserver/server_quic.go, and core/dnsserver/server_grpc.go call dns.Msg.Unpack without the dns.DefaultMsgAcceptFunc request policy used by UDP, TCP, and DNS-over-TLS. An unauthenticated client can send an RFC 2136 UPDATE that the proxy or forward plugin passes unchanged to an update-capable upstream. If that upstream trusts CoreDNS's source address or connection and does not require an attacker-unknown end-to-end TSIG, the request appears to originate from CoreDNS and can add, replace, or delete DNS records, redirect traffic, take over names, alter mail routing, or disrupt the writable zone. This issue is fixed in version 1.14.7.

CVSS 7.5 · High · EPSS 0.4%

Published

2026-09-16T18:39:22.955Z

Updated

2026-09-17T19:25:42.634Z

Stack: network

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