What is CVE-2026-31957?

CVE-2026-31957 is a critical-severity vulnerability in Himmelblau-Idm Himmelblau, classified under Initialization of a Resource with an Insecure Default. CVSS score: 10.0/10. Published 2026-03-11.

How severe is CVE-2026-31957?

Critical severity. CVSS v3 base score is 10.0 out of 10.

RCE in Himmelblau-Idm Himmelblau

CVE-2026-31957

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.

Published 2026-03-11 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 10.0 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.007 (52.5th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 53rd percentile — 52.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.005 · newest: 0.007 · change: +0.002

Affected products

Himmelblau-Idm Himmelblau — versions >= 3.0.0, < 3.1.0

Weakness classification (CWE)

CWE-1188 — Initialization of a Resource with an Insecure Default

References

github.com/himmelblau-idm/himmelblau/security/advisories/GHSA-q746-m2wv-qh4v (Mitigation, Vendor Advisory)

Frequently asked questions

What is CVE-2026-31957?: CVE-2026-31957 is a critical-severity vulnerability in Himmelblau-Idm Himmelblau, classified under Initialization of a Resource with an Insecure Default. CVSS score: 10.0/10. Published 2026-03-11.
How severe is CVE-2026-31957?: Critical severity. CVSS v3 base score is 10.0 out of 10.