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CVE-2026-31957— Himmelblau unset domain configuration can allow any-tenant authentication at first login for remote deployments

Quick assessment

Affected
himmelblau-idm himmelblau
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Himmelblau是Himmelblau开源的一个 Azure Entra ID 身份验证模块。 Himmelblau 3.1.0之前版本存在安全漏洞，该漏洞源于未配置租户域时身份验证不受租户范围限制，可能导致接受任意Entra ID域的身份验证尝试。

CVSS 10.0 · Critical EPSS 0.76% · P54

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-31957

Vulnerability Information
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Vulnerability Title
Himmelblau unset domain configuration can allow any-tenant authentication at first login for remote deployments
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
不安全的默认资源初始化
Source: CVE Program / CVE List V5
Vulnerability Title
Himmelblau 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Himmelblau是Himmelblau开源的一个 Azure Entra ID 身份验证模块。 Himmelblau 3.1.0之前版本存在安全漏洞，该漏洞源于未配置租户域时身份验证不受租户范围限制，可能导致接受任意Entra ID域的身份验证尝试。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

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Affected Products

Vendor Product Affected Versions CPE Subscribe
himmelblau-idm himmelblau >= 3.0.0, < 3.1.0 -

II. Public POCs for CVE-2026-31957

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III. Intelligence Information for CVE-2026-31957

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Vendor Advisories for CVE-2026-31957 (1)

IV. Related Vulnerabilities

Same product: himmelblau
Same vendor: himmelblau-idm
Same weakness: CWE-1188

V. Comments for CVE-2026-31957

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