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Incorrect AuthorizationWeakness · CWE-863

CVE-2026-45108

HIGH · 8.4 CVSS v3.1 Published 2026-05-27
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
90/100
Remediation priority · Urgent
Remotely reachable Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Himmelblau is an interoperability suite for Microsoft Azure Entra ID and Intune. From 2.0.0 to before 3.1.5 and 2.3.11, Himmelblau contained an authentication bypass vulnerability in the Device Authorization Grant (DAG) flow that allowed a user within the same Entra ID domain to obtain a local Unix session as another user by providing their own valid credentials. The vulnerability existed in the token_validate function, which validated domain aliases for legitimate multi-domain scenarios but failed to verify that the local part (username) of the authenticated user's UPN matched the requested account username. The function only compared domains, not the complete usernames. This vulnerability is fixed in 3.1.5 and 2.3.11.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Himmelblau versions 2.0.0 through 3.1.4 and before 2.3.11 contained an authentication bypass in the Device Authorization Grant flow where the token_validate function validated domain aliases but failed to verify that the local username portion of the authenticated user's UPN matched the requested account username, allowing privilege escalation to obtain local Unix sessions as other users within the same Entra ID domain.

MitigationUpgrade Himmelblau to version 3.1.5 or 2.3.11 or later, which includes the fix that properly validates the complete UPN including the username portion.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
Low
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
Low

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check if Himmelblau is installed
    Run 'himmelblau --version' or check for the binary at /usr/bin/himmelblau, or look for the service configuration in /etc/himmelblau/
    Affected if Himmelblau is not installed or not found on the system
  2. Determine installed Himmelblau version
    Run 'himmelblau --version' and note the version number output
    Affected if Version is between 2.0.0 and 3.1.4 inclusive, or is 2.x.x before 2.3.11, meaning it falls within 2.0.0 through 3.1.4 or before 2.3.11
  3. Check if Device Authorization Grant is enabled
    Examine Himmelblau configuration files in /etc/himmelblau/ for device_authorization_grant settings or look for oauth2/device scope configuration
    Affected if Device Authorization Grant flow is enabled in the configuration
  4. Verify token_validate configuration for UPN username matching
    Inspect /etc/himmelblau/ configuration files for token_validate or auth validation settings; check if strict UPN username verification is configured
    Affected if Token validation is configured to allow domain alias matching without enforcing that the local username portion of the UPN matches the requested account username

You are affected if Himmelblau is installed with a version in the range 2.0.0 through 3.1.4 or below 2.3.11, and the Device Authorization Grant flow is enabled with token validation that does not verify the full UPN including the local username portion.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Himmelblau to version 3.1.5 or 2.3.11 or later, which includes the fix that properly validates the complete UPN including the username portion.

Recommended fix High confidence

Upgrade to Himmelblau 3.1.5 (if on 3.x) or 2.3.11 (if on 2.x)

  1. Identify the currently installed Himmelblau version by checking the package manager or running `himmelblau --version`
  2. Review the current major version line (2.x or 3.x) to determine the appropriate upgrade path
  3. For Himmelblau 3.x versions: upgrade to version 3.1.5 or later
  4. For Himmelblau 2.x versions: upgrade to version 2.3.11 or later
  5. Verify the upgrade was successful by running `himmelblau --version`
  6. Test the Device Authorization Grant (DAG) flow to confirm the fix works correctly
  7. Review token_validate function behavior if possible to confirm username validation is now enforced
Caveat Review release notes for any breaking changes between current version and target fixed version before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-45108 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data