CoreDNS has TSIG authentication bypass on gRPC and QUIC transports

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.2 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-35579: 0.61% estimated exploitation activity in the next 30 days; percentile 49.29 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The gRPC, QUIC, DoH, and DoH3 transports in CoreDNS incorrectly handle TSIG authentication. For gRPC and QUIC, CoreDNS checks whether the TSIG key name exists in the config, but does not actually verify the TSIG HMAC. If the key name matches, tsigStatus remains nil and the tsig plugin treats the request as "verified". For DoH and DoH3, the issue is worse: TSIG is not verified at all. The DoH response writer has TsigStatus() hardcoded to return nil, so any request containing a TSIG record is treated as authenticated, even if the key name is invalid and the MAC is garbage. As a result, attackers may bypass TSIG authentication on affected transports and access TSIG-protected functionality such as AXFR/IXFR zone transfers, dynamic updates, or other TSIG-gated plugin behavior. Details In servergrpc.go and serverquic.go, the TSIG handling checks whether the TSIG key name exists, but does not call dns.TsigVerify(). Relevant code before fix: This means that for gRPC and QUIC, a…

Published by the source

28 Apr 2026, 22:54 UTC

Last modified by the source

8 May 2026, 15:31 UTC

Source last checked

26 Oct 2026, 15:20 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-vp29-5652-4fw9

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# Patch Next advisory brief: CVE-2026-35579

Advisory: CoreDNS has TSIG authentication bypass on gRPC and QUIC transports
IDs: CVE-2026-35579, GHSA-vp29-5652-4fw9
Record: https://patchnext.com/advisories/cve-2026-35579 (revision 1, source checked 26 Oct 2026, 15:20 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
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 1.14.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/coredns/coredns: affected < 1.14.3; fixed in 1.14.3

## 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://github.com/advisories/GHSA-vp29-5652-4fw9 (GitHub-reviewed advisory GHSA-vp29-5652-4fw9 lists affected ranges: Go github.com/coredns/coredns >=0 <1.14.3)

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