# CVE-2026-80854: usb: gadget: f_tcm: keep port count until LUN teardown completes

> A race condition in the Linux kernel USB gadget driver allows a use-after-free, potentially causing a system crash or arbitrary code execution.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-99537, BELL-CVE-2026-80854, DEBIAN-CVE-2026-80854, GHSA-g824-q393-34qq, UBUNTU-CVE-2026-80854

## What is CVE-2026-80854?

CVE-2026-80854 is an use after free vulnerability in Linux, published on 4 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_tcm: keep port count until LUN teardown completes

tcm_usbg_drop_nexus() permits session removal once tpg_port_count
reaches zero. However, usbg_port_unlink() currently decrements that
count from the fabric_pre_unlink() callback, before core_dev_del_lun()
waits for active se_lun references to drain.

If removal of the last LUN races a nexus removal, the latter can observe
a zero port count and call target_remove_session(). This frees
sess_cmd_map while an in-flight struct usbg_cmd, including its work item,
can still be accessed.

Overlapping the last-LUN unlink with nexus removal reproduces this
lifetime violation as a DEBUG_OBJECTS "free active" warning for
usbg_cmd_work, followed by a target-core BUG/Oops.

The generic target-core unlink path has no callback after
core_dev_del_lun() completes. Add an optional fabric_post_unlink()
callback and use it for the f_tcm port count. The count now remains
nonzero until core_dev_del_lun() has finished draining active LUN
references, preventing nexus removal from freeing the session during
command completion.

## Which versions are affected by CVE-2026-80854?


## How do I fix CVE-2026-80854?

Apply the vendor's patch.

## Is CVE-2026-80854 being exploited?

There is no known exploitation of CVE-2026-80854 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80854 and fix it if it is affected.

What it is: CVE-2026-80854 is an use after free vulnerability in Linux, published on 4 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-2026-80854 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-2026-80854/ (Markdown: https://insights.sbomify.com/CVE-2026-80854/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80854
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80854
- OSV: https://osv.dev/vulnerability/CVE-2026-80854

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80854/
Summaries are generated and may contain mistakes; the official description above is the record.