CVE-2026-31957Network attack vector

Unauthenticated host access via dynamic tenant registration

Published Mar 11, 2026 · Updated Mar 11, 2026

Authentication bypass in Himmelblau 3.0.0 through 3.0.1 allows remote attackers to obtain Linux host access using another Entra tenant. When the global domain is unset in /etc/himmelblau/himmelblau.conf, himmelblaud dynamically registers the first successful tenant provider and persists its details in the cache. Exposure requires a remote PAM path such as SSH during the unscoped install window; group mappings can turn cross-tenant login into root-equivalent access.

CVSS severity10.0
Critical
EPSS probability0.50%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Himmelblau 3.0.0 through 3.0.1 allows remote attackers to obtain Linux host access using another Entra tenant. When the global domain is unset in /etc/himmelblau/himmelblau.conf, himmelblaud dynamically registers the first successful tenant provider and persists its details in the cache. Exposure requires a remote PAM path such as SSH during the unscoped install window; group mappings can turn cross-tenant login into root-equivalent access.

The record

CVE
CVE-2026-31957
Published
Mar 11, 2026
Updated
Mar 11, 2026
Vendor
Himmelblau
Product
Himmelblau
Classifications
CWE-1188, T1078.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 11, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 3.0.0, < 3.1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Himmelblau · Himmelblauversion=>= 3.0.0, < 3.1.0

Published CVSS scores

10.0GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1188Initialization of a Resource with an Insecure Default
T1078.004Cloud Accounts

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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