Himmelblau unset domain configuration can allow any-tenant authentication at first login for remote deployments

{
  "id": "f0abae0c1f6c9f8fb52532a0463c27234dc093d9262ba1c17eddd56a02b76530",
  "url": "https://osv.dev/vulnerability/CVE-2026-31957",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Himmelblau unset domain configuration can allow any-tenant authentication at first login for remote deployments",
    "summary": "Himmelblau is an interoperability suite for Microsoft Azure Entra ID and Intune. From 3.0.0 to before 3.1.0, if Himmelblau is deployed without a configured tenant domain in himmelblau.conf, authentication is not tenant-scoped. In this mode, Himmelblau can accept authentication attempts for arbitrary Entra ID domains by dynamically registering providers at runtime. This behavior is intended for initial/local bootstrap scenarios, but it can create risk in remote authentication environments. This vulnerability is fixed in 3.1.0.",
    "evidence": "osv:CVE-2026-31957",
    "products": [],
    "severity": "critical",
    "structured": {
      "id": "CVE-2026-31957",
      "aliases": [
        "CVE-2026-31957",
        "GHSA-q746-m2wv-qh4v"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/himmelblau-idm/himmelblau",
              "type": "GIT",
              "events": [
                {
                  "introduced": "f6b4beed26b55d02a81fb064b0a21fb059aa99fe"
                },
                {
                  "fixed": "9079a98b44beb1c4e77215a262b95e6fd44c1dfb"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "3.0.0"
                      },
                      {
                        "fixed": "3.1.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "cpe": "cpe:2.3:a:himmelblau-idm:himmelblau:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "3.1.0"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "3.0.1",
            "3.0.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31957.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:50.255615235Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31957.json",
        "https://github.com/himmelblau-idm/himmelblau/security/advisories/GHSA-q746-m2wv-qh4v",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-31957"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-1188"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31957.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-31957",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 518870,
  "published_at": "2026-03-11T19:25:21.23+00:00"
}