Vulnerability-Lookup

GHSA-QHMP-Q7XH-99RH

Vulnerability from github – Published: 2026-04-28 22:46 – Updated: 2026-05-08 15:28

Summary

CoreDNS has TSIG authentication bypass on DoT, DoH, DoH3, DoQ, and gRPC

Details

Summary

CoreDNS' tsig plugin can be bypassed on non-plain-DNS transports because it trusts the transport writer's TsigStatus() instead of performing verification itself. In the attached PoC, plain DNS/TCP correctly rejects an invalid TSIG (NOTAUTH), while the same invalid-TSIG request is accepted over DoT (tls://) and DoH (https://), allowing a client without the shared secret to satisfy require all. The same bug class affects DoH3, DoQ, and gRPC.

Details

The tsig plugin decides whether an incoming TSIG was valid by consulting w.TsigStatus(): tsigStatus := w.TsigStatus(); if tsigStatus != nil { ... NOTAUTH ... } (plugin/tsig/tsig.go)

Two affected transports are shown directly in the PoC: - DoH: DoHWriter.TsigStatus() always returns nil (core/dnsserver/https.go), and the HTTP server passes unpacked DNS messages directly into the plugin chain. - DoT: the TLS server builds a dns.Server without setting TsigSecret (core/dnsserver/server_tls.go), unlike plain DNS/TCP/UDP which sets TsigSecret: s.tsigSecret (core/dnsserver/server.go).

The same transport-family bug pattern also appears on other transports: - DoH3 reuses the DoH writer path (core/dnsserver/server_https3.go -> core/dnsserver/https.go), so it inherits the same TsigStatus() == nil behavior. - DoQ uses DoQWriter.TsigStatus() error { return nil } (core/dnsserver/quic.go). - gRPC uses gRPCresponse.TsigStatus() error { return nil } (core/dnsserver/server_grpc.go).

The attached PoC was kept deliberately small (baseline TCP+DoT+DoH only) for convenience.

PoC

Adjust COREDNS_BIN in the PoC to point at right path (see the top-level const definitions for tunables as well)
Run python3 ./tsig-repro.py
Expected output: *** Start CoreDNS *** Corefile: /tmp/vh-f001-tsig-doh-dot-bypass/Corefile Log: /tmp/vh-f001-tsig-doh-dot-bypass/coredns.log

*** Baseline (plain TCP) *** no_tsig rcode=5 (expected REFUSED=5) invalid_tsig rcode=9 (expected NOTAUTH=9)

*** Candidate (DoT) *** no_tsig rcode=5 (expected REFUSED=5) invalid_tsig rcode=0 ancount=1 (expected NOERROR=0 and ancount>0)

*** Candidate (DoH) *** no_tsig http=200 rcode=5 (expected REFUSED=5) invalid_tsig http=200 rcode=0 ancount=1 (expected NOERROR=0 and ancount>0)

*** OK *** TSIG bypass reproduced: plain TCP rejects invalid TSIG, while DoT and DoH accept it. Results: /tmp/vh-f001-tsig-doh-dot-bypass/results.json

Impact

Unauthenticated remote clients can bypass TSIG-based authentication/authorization on first-class encrypted transports, enabling access to whatever the deployment intended to restrict behind tsig { require all } (e.g., zone data/privileged queries, etc.).

Severity ?

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

8.7 (High)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/coredns/coredns"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.14.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-33190"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-287",
      "CWE-303"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-28T22:46:15Z",
    "nvd_published_at": "2026-05-05T20:16:36Z",
    "severity": "HIGH"
  },
  "details": "### Summary\nCoreDNS\u0027 tsig plugin can be bypassed on non-plain-DNS transports because it trusts the transport writer\u0027s TsigStatus() instead of performing verification itself. In the attached PoC, plain DNS/TCP correctly rejects an invalid TSIG (NOTAUTH), while the same invalid-TSIG request is accepted over DoT (tls://) and DoH (https://), allowing a client without the shared secret to satisfy require all. The same bug class affects DoH3, DoQ, and gRPC.\n\n### Details\nThe tsig plugin decides whether an incoming TSIG was valid by consulting w.TsigStatus(): tsigStatus := w.TsigStatus(); if tsigStatus != nil { ... NOTAUTH ... } (plugin/tsig/tsig.go)\n\nTwo affected transports are shown directly in the PoC:\n- DoH: DoHWriter.TsigStatus() always returns nil (core/dnsserver/https.go), and the HTTP server passes unpacked DNS messages directly into the plugin chain.\n- DoT: the TLS server builds a dns.Server without setting TsigSecret (core/dnsserver/server_tls.go), unlike plain DNS/TCP/UDP which sets TsigSecret: s.tsigSecret (core/dnsserver/server.go).\n\nThe same transport-family bug pattern also appears on other transports:\n- DoH3 reuses the DoH writer path (core/dnsserver/server_https3.go -\u003e core/dnsserver/https.go), so it inherits the same TsigStatus() == nil behavior.\n- DoQ uses DoQWriter.TsigStatus() error { return nil } (core/dnsserver/quic.go).\n- gRPC uses gRPCresponse.TsigStatus() error { return nil } (core/dnsserver/server_grpc.go).\n\nThe attached PoC was kept deliberately small (baseline TCP+DoT+DoH only) for convenience.\n\n### PoC\n1. Adjust COREDNS_BIN in the PoC to point at right path (see the top-level const definitions for tunables as well)\n2. Run python3 ./tsig-repro.py\n3. Expected output:\n*** Start CoreDNS ***\nCorefile: /tmp/vh-f001-tsig-doh-dot-bypass/Corefile\nLog: /tmp/vh-f001-tsig-doh-dot-bypass/coredns.log\n\n*** Baseline (plain TCP) ***\nno_tsig rcode=5 (expected REFUSED=5)\ninvalid_tsig rcode=9 (expected NOTAUTH=9)\n\n*** Candidate (DoT) ***\nno_tsig rcode=5 (expected REFUSED=5)\ninvalid_tsig rcode=0 ancount=1 (expected NOERROR=0 and ancount\u003e0)\n\n*** Candidate (DoH) ***\nno_tsig http=200 rcode=5 (expected REFUSED=5)\ninvalid_tsig http=200 rcode=0 ancount=1 (expected NOERROR=0 and ancount\u003e0)\n\n*** OK ***\nTSIG bypass reproduced: plain TCP rejects invalid TSIG, while DoT and DoH accept it.\nResults: /tmp/vh-f001-tsig-doh-dot-bypass/results.json\n\n\n### Impact\nUnauthenticated remote clients can bypass TSIG-based authentication/authorization on first-class encrypted transports, enabling access to whatever the deployment intended to restrict behind tsig { require all } (e.g., zone data/privileged queries, etc.).",
  "id": "GHSA-qhmp-q7xh-99rh",
  "modified": "2026-05-08T15:28:24Z",
  "published": "2026-04-28T22:46:15Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/coredns/coredns/security/advisories/GHSA-qhmp-q7xh-99rh"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33190"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/coredns/coredns"
    },
    {
      "type": "WEB",
      "url": "https://github.com/coredns/coredns/releases/tag/v1.14.3"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "CoreDNS has TSIG authentication bypass on DoT, DoH, DoH3, DoQ, and gRPC"
}

CVE-2026-33190 (GCVE-0-2026-33190)

Vulnerability from cvelistv5 – Published: 2026-05-05 19:02 – Updated: 2026-05-06 12:47

Title

CoreDNS TSIG authentication bypass on encrypted DNS transports

Summary

CoreDNS is a DNS server that chains plugins. In versions prior to 1.14.3, the tsig plugin can be bypassed on non-plain-DNS transports (DoT, DoH, DoH3, DoQ, and gRPC) because it trusts the transport writer's TsigStatus() instead of performing verification itself. The DoH and DoH3 writer's TsigStatus() always returns nil, the DoT server does not set TsigSecret on the dns.Server, and the DoQ and gRPC writers also unconditionally return nil. This allows an unauthenticated remote client to bypass TSIG-based authentication and access resources intended to be restricted behind a tsig require all policy. Plain DNS over TCP and UDP are not affected. This issue has been fixed in version 1.14.3.

Severity ?

8.7 (High)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

CWE

CWE-303 - Incorrect Implementation of Authentication Algorithm

Assigner

GitHub_M

References

2 references

URL	Tags
https://github.com/coredns/coredns/security/advis…	x_refsource_CONFIRM
https://github.com/coredns/coredns/releases/tag/v1.14.3	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
coredns	coredns	Affected: < 1.14.3

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-33190",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-05-06T12:46:45.291268Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-05-06T12:47:07.338Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/coredns/coredns/security/advisories/GHSA-qhmp-q7xh-99rh"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "coredns",
          "vendor": "coredns",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 1.14.3"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "CoreDNS is a DNS server that chains plugins. In versions prior to 1.14.3, the tsig plugin can be bypassed on non-plain-DNS transports (DoT, DoH, DoH3, DoQ, and gRPC) because it trusts the transport writer\u0027s TsigStatus() instead of performing verification itself. The DoH and DoH3 writer\u0027s TsigStatus() always returns nil, the DoT server does not set TsigSecret on the dns.Server, and the DoQ and gRPC writers also unconditionally return nil. This allows an unauthenticated remote client to bypass TSIG-based authentication and access resources intended to be restricted behind a tsig require all policy. Plain DNS over TCP and UDP are not affected. This issue has been fixed in version 1.14.3."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 8.7,
            "baseSeverity": "HIGH",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "HIGH",
            "vulnIntegrityImpact": "NONE"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-303",
              "description": "CWE-303: Incorrect Implementation of Authentication Algorithm",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-05T19:02:55.374Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/coredns/coredns/security/advisories/GHSA-qhmp-q7xh-99rh",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/coredns/coredns/security/advisories/GHSA-qhmp-q7xh-99rh"
        },
        {
          "name": "https://github.com/coredns/coredns/releases/tag/v1.14.3",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/coredns/coredns/releases/tag/v1.14.3"
        }
      ],
      "source": {
        "advisory": "GHSA-qhmp-q7xh-99rh",
        "discovery": "UNKNOWN"
      },
      "title": "CoreDNS TSIG authentication bypass on encrypted DNS transports"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-33190",
    "datePublished": "2026-05-05T19:02:55.374Z",
    "dateReserved": "2026-03-17T22:16:36.721Z",
    "dateUpdated": "2026-05-06T12:47:07.338Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

GHSA-QHMP-Q7XH-99RH

Summary

Details

PoC

Impact

CVE-2026-33190 (GCVE-0-2026-33190)

Tags

Sightings

Nomenclature