# CVE-2026-90323: ublk: validate auto buf reg before taking uring_cmd

> A local attacker can cause a kernel hang during teardown by triggering a validation error in ublk auto buffer registration.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-90323, DEBIAN-CVE-2026-90323, GHSA-rq26-mw8f-3hjh, UBUNTU-CVE-2026-90323

## What is CVE-2026-90323?

CVE-2026-90323 is a denial of service 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:

ublk: validate auto buf reg before taking uring_cmd

With UBLK_F_AUTO_BUF_REG, invalid sqe->addr can fail after
ublk_fill_io_cmd() has set UBLK_IO_FLAG_ACTIVE. The uring_cmd is
completed while the tag stays active, which can hang teardown.

Split validation from buffer apply so the check has no side effects,
then take the uring_cmd and store the already-validated buffer. Apply
the same order in FETCH so io->buf is not written before __ublk_fetch()
state checks.

## Which versions are affected by CVE-2026-90323?


## How do I fix CVE-2026-90323?

Apply the vendor's patch.

## Is CVE-2026-90323 being exploited?

There is no known exploitation of CVE-2026-90323 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90323 and fix it if it is affected.

What it is: CVE-2026-90323 is a denial of service 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-2026-90323 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-2026-90323/ (Markdown: https://insights.sbomify.com/CVE-2026-90323/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90323
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90323
- OSV: https://osv.dev/vulnerability/CVE-2026-90323

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90323/
Summaries are generated and may contain mistakes; the official description above is the record.