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

Critical 10.0 Published 11 Mar 2026 Updated 12 Mar 2026

Attackers can authenticate against arbitrary Azure Entra ID domains if the tenant domain is unset, enabling unauthorized access in remote deployments.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

What is CVE-2026-31957?

CVE-2026-31957 is a critical authentication bypass vulnerability in himmelblau-idm himmelblau, published on 11 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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.

Weakness: CWE-1188

Which versions are affected by CVE-2026-31957?

It affects 1 product.

Products include Himmelblau-Idm Himmelblau.

How do I fix CVE-2026-31957?

No fix has been published for CVE-2026-31957 yet. Limit exposure of the affected software until one is available.

Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.

Is CVE-2026-31957 being exploited?

There is no known exploitation of CVE-2026-31957 in the wild and no public exploit code.

Sources

Also known as GHSA-q746-m2wv-qh4v.