CVE-2026-86003 CoreDNS DoH/DoQ/gRPC bypass UPDATE rejection enforced on UDP/TCP
Unauthenticated attackers can bypass UPDATE rejection in CoreDNS DoH/DoQ/gRPC listeners to modify DNS records if upstream trusts CoreDNS.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-86003?
CVE-2026-86003 is a high-severity missing authorization vulnerability in coredns, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-441
Which versions are affected by CVE-2026-86003?
3 open source packages ship an affected version, including github.com/coredns/coredns.
| Package | Affected | Fixed in |
|---|---|---|
github.com/coredns/coredns Go | All versions | 1.14.7 |
github.com/coredns/coredns Go | All versions | 1.14.7 |
github.com/coredns/coredns Go | All versions | 1.14.7 |
How do I fix CVE-2026-86003?
Upgrade github.com/coredns/coredns to 1.14.7 or later.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-86003 being exploited?
There is no known exploitation of CVE-2026-86003 in the wild and no public exploit code.
Sources
Also known as AZL-101835, CLEANSTART-2026-GT82113, ECHO-5dd9-46b5-527a, GHSA-9gm5-9rfh-m6vx, GO-2026-6506, MINI-2qj5-mfrw-74r4 and 19 more.