fkie_cve-2026-82399

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 request paths in plugin/pkg/doh/doh.go, core/dnsserver/server_quic.go, and core/dnsserver/server_grpc.go call dns.Msg.Unpack on attacker-controlled DNS section counts before dns.DefaultMsgAcceptFunc validates the fixed header. An unauthenticated client can use DNS name compression and excessive section counts to amplify allocation before the plugin chain, so plugin-level rate limiting cannot prevent concurrent requests from exhausting memory and terminating CoreDNS. The ordinary UDP and TCP listeners are not affected because they validate the header first. This issue is fixed in version 1.14.7.

GHSA-mrg3-qvqr-jw29 — CoreDNS: Unauthenticated memory exhaustion in custom transports

Affected: Go: github.com/coredns/coredns

### Summary

CoreDNS parses attacker-controlled DNS section counts before validating them on DNS-over-HTTPS (DoH and DoH3), DNS-over-QUIC (DoQ), and DNS-over-gRPC listeners. An unauthenticated client can use DNS name compression to make one 65,533-byte request allocate more than 10 MiB while it is unpacked. Concurrent requests can exhaust memory and terminate CoreDNS.

### Details

The affected request paths call `dns.Msg.Unpack` directly:

- [DoH POST and GET decoding](https://github.com/coredns/coredns/blob/18a58b9e898ccd95c3f8ee72a37b95b3d1e3e928/plugin/pkg/doh/doh.go#L134-L155). DoH3 uses the same decoder. - [DoQ stream handling](https://github.com/coredns/coredns/blob/18a58b9e898ccd95c3f8ee72a37b95b3d1e3e928/core/dnsserver/server_quic.go#L212-L219). - [DNS-over-gRPC query handling](https://github.com/coredns/coredns/blob/18a58b9e898ccd95c3f8ee72a37b95b3d1e3e928/core/dnsserver/server_grpc.go#L176-L184).

This differs from the [miekg/dns](https://github.com/miekg/dns) UDP and TCP server. Its [`serveDNS`](https://github.com/miekg/dns/blob/v1.1.72/server.go#L628-L643) path decodes the fixed 12-byte header and invokes [`DefaultMsgAcceptFunc`](https://github.com/miekg/dns/blob/v1.1.72/acceptfunc.go#L33-L57) before unpacking the DNS sections. The default policy rejects requests unless `QDCOUNT` is exactly one and also limits the other section counts. CoreDNS's custom transports bypass this early validation.

Parsing happens before the plugin chain. Plugin-level rate limiting o…

Most recent entries from all

bdu:2026-14834

fkie_cve-2026-82399

GHSA-mrg3-qvqr-jw29 — CoreDNS: Unauthenticated memory exhaustion in custom transports