# CVE-2026-90097: Drivers: hv: vmbus: Skip VMBus module cleanup for non-nested root partition

> A local attacker with high privileges can trigger a kernel panic by unloading the VMBus module in a non-nested root partition, causing denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-102971, BELL-CVE-2026-90097, DEBIAN-CVE-2026-90097, GHSA-m2q7-q8rx-27pr, UBUNTU-CVE-2026-90097

## What is CVE-2026-90097?

CVE-2026-90097 is a vulnerability in Linux, published on 17 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

Drivers: hv: vmbus: Skip VMBus module cleanup for non-nested root partition

The VMBus module initialization function, hv_acpi_init(), currently
does nothing when running in the root partition and root is not nested
in another VM. But the initialization function reports success, so the
VMBus module is indeed loaded. VMBus functionality is not actually
needed, but the VMBus module must be loaded so that hv_vmbus_exists()
can answer correctly. Furthermore, the mshv_root dependency on the
VMBus module is needed as described in the commit message for
840b740a35bf ("mshv: Add conditional VMBus dependency").

Loading the VMBus module without actually initializing it causes
failures if the module should later be unloaded. The module unload code
tries to clean up things that were never initialized, resulting in
memory faults and a panic.

Fix this by having VMBus module exit function perform the same
check for non-nested root partition, and do nothing in such a
case, just like hv_acpi_init().

In the long run, the code that manages the Hyper-V provided SynIC
should be refactored to better coordinate the requirements of
root partition scenarios and normal VM scenarios, and to hopefully
remove the hv_vmbus_exists() dependnecy between mshv_root and
VMBus modules. Preventing the current unload failure scenario is
an expediency until such a refactoring is done.

## Which versions are affected by CVE-2026-90097?


## How do I fix CVE-2026-90097?

Apply the vendor's patch.

## Is CVE-2026-90097 being exploited?

There is no known exploitation of CVE-2026-90097 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90097 and fix it if it is affected.

What it is: CVE-2026-90097 is a vulnerability in Linux, published on 17 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-90097 in the wild and no public exploit code.

Affected product: Linux. 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-2026-90097/ (Markdown: https://insights.sbomify.com/CVE-2026-90097/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90097
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90097
- OSV: https://osv.dev/vulnerability/CVE-2026-90097

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90097/
Summaries are generated and may contain mistakes; the official description above is the record.