Vulnerability-Lookup

GHSA-8FWW-64WC-46PF

Vulnerability from github – Published: 2026-08-21 12:30 – Updated: 2026-08-21 12:30

Details

Improper authentication in the agent receiver of Checkmk <2.5.0p10 allows an unauthenticated remote attacker to bypass mutual TLS client certificate verification of relay endpoints by supplying a fixed placeholder identity in the request URL, resulting in limited impact on integrity and availability. Only the Cloud, Ultimate and Ultimate MT editions are affected, as other editions do not expose relay endpoints.

Severity

6.9 (Medium)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-15576"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-306"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-21T11:17:04Z",
    "severity": "MODERATE"
  },
  "details": "Improper authentication in the agent receiver of Checkmk \u003c2.5.0p10 allows an unauthenticated remote attacker to bypass mutual TLS client certificate verification of relay endpoints by supplying a fixed placeholder identity in the request URL, resulting in limited impact on integrity and availability. Only the Cloud, Ultimate and Ultimate MT editions are affected, as other editions do not expose relay endpoints.",
  "id": "GHSA-8fww-64wc-46pf",
  "modified": "2026-08-21T12:30:32Z",
  "published": "2026-08-21T12:30:32Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-15576"
    },
    {
      "type": "WEB",
      "url": "https://checkmk.com/werk/20174"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
      "type": "CVSS_V4"
    }
  ]
}

CVE-2026-15576 (GCVE-0-2026-15576)

Vulnerability from cvelistv5 – Published: 2026-08-21 11:10 – Updated: 2026-08-21 11:53

Title

Agent receiver accepts mTLS requests without a client certificate

Summary

Severity

6.9 (Medium)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-21 11:53 UTC

CWE

CWE-306 - Missing Authentication for Critical Function

Assigner

Checkmk mitre root

References

1 reference

URL	Tags
https://checkmk.com/werk/20174	vendor-advisory

Impacted products

1 product

Vendor	Product	Version
Checkmk GmbH	Checkmk	Affected: 2.5.0 , < 2.5.0p10 (semver) cpe:2.3:a:checkmk:checkmk::::::::

Credits

PS Positive Security GmbH

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JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-15576",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-21T11:53:35.618102Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-21T11:53:45.355Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Checkmk",
          "vendor": "Checkmk GmbH",
          "versions": [
            {
              "lessThan": "2.5.0p10",
              "status": "affected",
              "version": "2.5.0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:a:checkmk:checkmk:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "2.5.0p10",
                  "versionStartIncluding": "2.5.0",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "reporter",
          "value": "PS Positive Security GmbH"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Improper authentication in the agent receiver of Checkmk \u003c2.5.0p10 allows an unauthenticated remote attacker to bypass mutual TLS client certificate verification of relay endpoints by supplying a fixed placeholder identity in the request URL, resulting in limited impact on integrity and availability. Only the Cloud, Ultimate and Ultimate MT editions are affected, as other editions do not expose relay endpoints."
        }
      ],
      "impacts": [
        {
          "capecId": "CAPEC-115",
          "descriptions": [
            {
              "lang": "en",
              "value": "CAPEC-115: Authentication Bypass"
            }
          ]
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "baseScore": 6.9,
            "baseSeverity": "MEDIUM",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N",
            "version": "4.0"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-306",
              "description": "CWE-306: Missing Authentication for Critical Function",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-21T11:10:00.856Z",
        "orgId": "f7d6281c-4801-44ce-ace2-493291dedb0f",
        "shortName": "Checkmk"
      },
      "references": [
        {
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://checkmk.com/werk/20174"
        }
      ],
      "title": "Agent receiver accepts mTLS requests without a client certificate",
      "x_generator": {
        "engine": "cvelib 1.8.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "f7d6281c-4801-44ce-ace2-493291dedb0f",
    "assignerShortName": "Checkmk",
    "cveId": "CVE-2026-15576",
    "datePublished": "2026-08-21T11:10:00.856Z",
    "dateReserved": "2026-07-13T08:39:03.953Z",
    "dateUpdated": "2026-08-21T11:53:45.355Z",
    "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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

GHSA-8FWW-64WC-46PF

CVE-2026-15576 (GCVE-0-2026-15576)

Tags

Sightings

Nomenclature