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VulnerabilityPublished Updated

CVE-2026-31957: himmelblau · Insecure Default Initialization of Resource

Affects himmelblauSource CVE Database V5

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Not known to be exploited · CVSS 10.0 Critical : upgrade to 3.1.0 as a priority.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 3.1 base score
10.0Critical
How severe the flaw is on the 0–10 CVSS scale.

Contested

Critical score, yet low EPSS after six months
EPSS
0.5% chance of exploitation in 30 days – higher than 44% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 3.1.0
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 11 Mar 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade himmelblau and himmelblau-idm/himmelblau to 3.1.0.

Affected software

ProductAffectedFixed in
himmelblau-idmhimmelblauAffected
  • >=3.0.0 <3.1.0
Fixed in
  • 3.1.0
GitHubhimmelblau-idm/himmelblaupkg:github/himmelblau-idm/himmelblauOther threatsAffected
  • <3.1.0 >=3.0.0
Fixed in
  • 3.1.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

To mitigate CVE-2026-31957, organizations should immediately upgrade himmelblau to version 3.1.0 or later, where the vulnerability is fixed. Until the upgrade can be applied, ensure that the tenant domain is explicitly configured in himmelblau.conf to prevent the system from accepting authentication requests from arbitrary domains. Review and audit current himmelblau deployments to verify tenant domain configuration settings. Implement network-level access controls to restrict access to himmelblau endpoints only to trusted sources. Monitor authentication logs for unusual or unexpected tenant domain authentication attempts. Additionally, enforce strict Azure Entra ID conditional access policies and multi-factor authentication to reduce the risk of unauthorized access. Conduct thorough penetration testing and security assessments post-mitigation to confirm the vulnerability is addressed. Maintain an incident response plan to quickly react to any suspicious authentication activity related to this vulnerability.

Description

CVE-2026-31957 is a critical vulnerability in himmelblau versions 3.0.0 up to but not including 3.1.0, an interoperability suite for Microsoft Azure Entra ID and Intune. The issue arises when himmelblau is deployed without a configured tenant domain in its configuration file, causing authentication to be unscoped to any tenant. This allows the system to accept authentication attempts for arbitrary Entra ID domains by dynamically registering providers at runtime, which is intended only for initial or local bootstrap scenarios. In remote authentication environments, this behavior can lead to unauthorized access, compromising confidentiality, integrity, and availability. The vulnerability has a CVSS score of 10.0, indicating critical severity, and is fixed in version 3.

References

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