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High, CVSS 7.5amended

CoreDNS: Unauthenticated memory exhaustion in custom transports

CVE-2026-82399GHSA-mrg3-qvqr-jw29

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (github.com/coredns/coredns 1.14.7), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS
  • CVE-2026-82399: 0.61% estimated exploitation activity in the next 30 days; percentile 49.21 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

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. DoH3 uses the same decoder. - DoQ stream handling. - DNS-over-gRPC query handling. This differs from the miekg/dns UDP and TCP server. Its serveDNS path decodes the fixed 12-byte header and invokes DefaultMsgAcceptFunc 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 or request handling cannot prevent the allocation.…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-mrg3-qvqr-jw29

  2. Revision 2 · amended ·

    Amended from osv record GO-2026-6507

  3. Revision 1 · created ·

    Published from osv record GHSA-mrg3-qvqr-jw29

Agent brief

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# Patch Next advisory brief: CVE-2026-82399

Advisory: CoreDNS: Unauthenticated memory exhaustion in custom transports
IDs: CVE-2026-82399, GHSA-mrg3-qvqr-jw29
Record: https://patchnext.com/advisories/cve-2026-82399 (revision 3, source checked 26 Oct 2026, 15:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/coredns/coredns 1.14.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/coredns/coredns: affected <= 1.14.6; fixed in 1.14.7

## Suggested inspection (read-only)
- Go github.com/coredns/coredns: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/coredns/coredns.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-mrg3-qvqr-jw29 (OSV record GHSA-mrg3-qvqr-jw29 lists affected ranges: Go github.com/coredns/coredns >=0 <1.14.7 (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6507 (OSV record GO-2026-6507 lists affected ranges: Go github.com/coredns/coredns >=0 <1.14.7 (fixed))
- Verified: https://github.com/advisories/GHSA-mrg3-qvqr-jw29 (GitHub-reviewed advisory GHSA-mrg3-qvqr-jw29 lists affected ranges: Go github.com/coredns/coredns >=0 <=1.14.6)

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