# CVE-2026-93121: usb: gadget: f_fs: Fix fence cleanup in ffs_dmabuf_transfer() error paths

> A flaw in the Linux kernel USB gadget driver causes undefined behavior when handling specific error paths, potentially leading to a system crash.

- **Severity:** High 7.0 (`CVSS:3.1/AV:L/AC:H/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:** 17 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-93121, DEBIAN-CVE-2026-93121, GHSA-vg86-rjrh-q8jw, UBUNTU-CVE-2026-93121

## What is CVE-2026-93121?

CVE-2026-93121 is a high-severity 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:

usb: gadget: f_fs: Fix fence cleanup in ffs_dmabuf_transfer() error paths

The error paths for endpoint-disabled (ESHUTDOWN) and request-allocation
failure (ENOMEM) in ffs_dmabuf_transfer() jump to err_fence_put which
calls dma_fence_put() on the fence. However, at that point the fence has
only been kmalloc'd — dma_fence_init() has not been called yet, so the
refcount and the fence ops are uninitialized. Calling dma_fence_put() on
such an object leads to undefined behavior.

Use kfree() instead, since the fence is just a plain allocation at this
stage, and rename the label to err_fence_free to reflect the actual
cleanup action.

## Which versions are affected by CVE-2026-93121?


## How do I fix CVE-2026-93121?

Apply the vendor's patch.

## Is CVE-2026-93121 being exploited?

There is no known exploitation of CVE-2026-93121 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93121 and fix it if it is affected.

What it is: CVE-2026-93121 is a high-severity 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-2026-93121 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-2026-93121/ (Markdown: https://insights.sbomify.com/CVE-2026-93121/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93121
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93121
- OSV: https://osv.dev/vulnerability/CVE-2026-93121

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93121/
Summaries are generated and may contain mistakes; the official description above is the record.