# CVE-2026-90206: nvmet: fix max_qid race between configfs and controller allocation

> A race condition in the Linux kernel nvmet subsystem allows local attackers to trigger memory corruption and potential code execution by modifying queue limits during controller allocation.

- **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-102641, BELL-CVE-2026-90206, DEBIAN-CVE-2026-90206, GHSA-6cwp-gq4q-qccv, UBUNTU-CVE-2026-90206

## What is CVE-2026-90206?

CVE-2026-90206 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:

nvmet: fix max_qid race between configfs and controller allocation

The function nvmet_subsys_attr_qid_max_store() can race against
nvmet_alloc_ctrl() when a subsystem's max_qid limit is modified.

Suppose max_qid is currently 64. If nvmet_alloc_ctrl() executes:
ctrl->sqs = kzalloc_objs(struct nvmet_sq *, subsys->max_qid + 1);
and at this exact point, a userspace process changes max_qid to 128,
nvmet_subsys_attr_qid_max_store() will set the new max_qid value. It
attempts to delete active controllers to force a reconnect, but the
new controller won't be deleted because it hasn't been added to the
subsys->ctrls list yet.

nvmet_alloc_ctrl() then proceeds and adds the new controller to the
subsys->ctrls list. Later, when nvmet_install_queue() is called, it
will see max_qid set to 128, but the memory allocated for sqs is only
sized for 64 entries. This results in a KASAN out-of-bounds warning
and potential memory corruptions.

Fix this by protecting the queue allocations and list insertion in
nvmet_alloc_ctrl() with down_read(&nvmet_config_sem). Because
nvmet_subsys_attr_qid_max_store() acquires down_write(&nvmet_config_sem)
to modify the attribute, this safely prevents the configfs writer from
modifying max_qid during controller creation.

Copy the max_qid from the subsystem to the controller's structure
during the allocation; ctrl->max_qid never changes as long as the
controller remains in LIVE state, so this will prevent similar race
conditions.

## Which versions are affected by CVE-2026-90206?


## How do I fix CVE-2026-90206?

Apply the vendor's patch.

## Is CVE-2026-90206 being exploited?

There is no known exploitation of CVE-2026-90206 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90206 and fix it if it is affected.

What it is: CVE-2026-90206 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-2026-90206 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-2026-90206/ (Markdown: https://insights.sbomify.com/CVE-2026-90206/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90206
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90206
- OSV: https://osv.dev/vulnerability/CVE-2026-90206

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90206/
Summaries are generated and may contain mistakes; the official description above is the record.