# 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.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Sep 2026
- **Updated:** 17 Sep 2026
- **Also known as:** AZL-101835, CLEANSTART-2026-GT82113, ECHO-5dd9-46b5-527a, GHSA-9gm5-9rfh-m6vx, GO-2026-6506, MINI-2qj5-mfrw-74r4, MINI-2r3r-c8j6-mcxr, MINI-427m-24w6-2q9p, MINI-6pw3-j29g-mg6v, MINI-6w66-wj49-fm99, MINI-7jjw-cvp4-89r9, MINI-82qw-cmpr-647x, MINI-c6c8-mf55-h9jv, MINI-ch2c-684w-f7r5, MINI-f27g-8c9j-6rxp, MINI-fcr9-6q3c-7rfq, MINI-fgqw-54g8-ccjh, MINI-g3pr-7f5q-p6xq, MINI-g6pw-7q6w-pp3m, MINI-h5fj-5866-g62h, MINI-jf8w-qmxc-mgq7, MINI-jhxw-669c-4p9m, MINI-m2gf-4h9c-p69w, MINI-w7gx-74wf-96jp, MINI-xfr3-97ph-g4g3

## 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 (Unintended Proxy or Intermediary)

## Which versions are affected by CVE-2026-86003?

3 open source packages ship an affected version, including github.com/coredns/coredns.


| Package | Ecosystem | 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.

## Is CVE-2026-86003 being exploited?

There is no known exploitation of CVE-2026-86003 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-86003 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-86003 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/coredns/coredns (Go): affected all versions; fixed in 1.14.7
- github.com/coredns/coredns (Go): affected all versions; fixed in 1.14.7
- github.com/coredns/coredns (Go): affected all versions; fixed in 1.14.7

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-86003/ (Markdown: https://insights.sbomify.com/CVE-2026-86003/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-86003
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-86003
- OSV: https://osv.dev/vulnerability/CVE-2026-86003

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-86003/
Summaries are generated and may contain mistakes; the official description above is the record.