# CVE-2026-45108: Himmelblau: Authentication Bypass via Cross-User Local Session Impersonation in Device Authorization Grant (DAG) Flow

> An attacker can impersonate another user to gain a local Unix session by exploiting a username validation flaw in the Device Authorization Grant flow.

- **Severity:** High 8.4 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 May 2026
- **Updated:** 28 May 2026
- **Also known as:** GHSA-pmxh-j4r6-88mv, SUSE-SU-2026:22186-1, openSUSE-SU-2026:21111-1

## What is CVE-2026-45108?

CVE-2026-45108 is a high-severity authentication bypass vulnerability in himmelblau-idm himmelblau, published on 27 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

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.

Weakness: CWE-863 (Incorrect Authorization)

## Which versions are affected by CVE-2026-45108?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `himmelblau` | SUSE:Linux Enterprise Server 16.0 | All versions | 2.3.11+git1.116c6763-160000.1.1 |
| `himmelblau` | SUSE:Linux Enterprise Server for SAP applications 16.0 | All versions | 2.3.11+git1.116c6763-160000.1.1 |
| `himmelblau` | openSUSE:Leap 16.0 | All versions | 2.3.11+git1.116c6763-160000.1.1 |

## How do I fix CVE-2026-45108?

Upgrade to a fixed version.

## Is CVE-2026-45108 being exploited?

There is no known exploitation of CVE-2026-45108 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-45108 and fix it if it is affected.

What it is: CVE-2026-45108 is a high-severity authentication bypass vulnerability in himmelblau-idm himmelblau, published on 27 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-45108 in the wild and no public exploit code.

Affected product: himmelblau-idm himmelblau. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-45108/ (Markdown: https://insights.sbomify.com/CVE-2026-45108/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45108
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45108
- OSV: https://osv.dev/vulnerability/CVE-2026-45108

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45108/
Summaries are generated and may contain mistakes; the official description above is the record.