# CVE-2026-90023: usb: gadget: f_mass_storage: fix null pointer dereference in fsg_common_set_num_buffers()

> A local attacker with access to USB gadget configuration can trigger a null pointer dereference in the Linux kernel, causing a system crash.

- **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:** 16 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-101490, BELL-CVE-2026-90023, DEBIAN-CVE-2026-90023, GHSA-4pqp-h39m-gcw4, UBUNTU-CVE-2026-90023

## What is CVE-2026-90023?

CVE-2026-90023 is a 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:

usb: gadget: f_mass_storage: fix null pointer dereference in fsg_common_set_num_buffers()

Previously fsg_num_buffers_validate() was removed as it was not
necessary due to Kconfig setting the limits for n from 2 to 256 with
default as 2. However, setting the page content in such a way that
kstrtou8() reflects n value as either 0 or 1 bypasses these
restrictions leading to a null pointer dereference if n is 0. Fix
this by adding a check for n < 2 and returning -EINVAL if n is
either 0 or 1 consistent with Kconfig logic.

## Which versions are affected by CVE-2026-90023?


## How do I fix CVE-2026-90023?

Apply the vendor's patch.

## Is CVE-2026-90023 being exploited?

There is no known exploitation of CVE-2026-90023 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90023 and fix it if it is affected.

What it is: CVE-2026-90023 is a 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-2026-90023 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-2026-90023/ (Markdown: https://insights.sbomify.com/CVE-2026-90023/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90023
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90023
- OSV: https://osv.dev/vulnerability/CVE-2026-90023

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90023/
Summaries are generated and may contain mistakes; the official description above is the record.