# CVE-2026-90009: scsi: bsg: Fix TOCTOU in io_uring passthrough command setup

> A time-of-check time-of-use race condition in the Linux kernel's SCSI BSG driver allows local attackers to trigger a buffer overflow and potentially execute code or escalate privileges.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 16 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-90009, GHSA-22qm-w4f2-g533, UBUNTU-CVE-2026-90009

## What is CVE-2026-90009?

CVE-2026-90009 is a high-severity vulnerability in Linux, published on 16 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:

scsi: bsg: Fix TOCTOU in io_uring passthrough command setup

scsi_bsg_uring_cmd() reads bsg_uring_cmd from the shared mmap'd SQE.
Userspace can change a field after we check it and before we use it.
request_len is the sharp case: it can grow past sizeof(scmd->cmnd) after
the bound check and overflow scmd->cmnd in copy_from_user().

READ_ONCE() the SQE fields we check or use into locals before use.

## Which versions are affected by CVE-2026-90009?


## How do I fix CVE-2026-90009?

Apply the vendor's patch.

## Is CVE-2026-90009 being exploited?

There is no known exploitation of CVE-2026-90009 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90009 and fix it if it is affected.

What it is: CVE-2026-90009 is a high-severity vulnerability in Linux, published on 16 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-2026-90009 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-2026-90009/ (Markdown: https://insights.sbomify.com/CVE-2026-90009/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90009
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90009
- OSV: https://osv.dev/vulnerability/CVE-2026-90009

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90009/
Summaries are generated and may contain mistakes; the official description above is the record.