# CVE-2025-40315: usb: gadget: f_fs: Fix epfile null pointer access after ep enable.

> A race condition in the Linux kernel USB gadget functionfs driver causes a null pointer dereference, leading to 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:** 8 Dec 2025
- **Updated:** 23 May 2026
- **Also known as:** BELL-CVE-2025-40315, DEBIAN-CVE-2025-40315, GHSA-xqq2-8462-xjg2, ROOT-OS-DEBIAN-12-CVE-2025-40315, ROOT-OS-DEBIAN-13-CVE-2025-40315, ROOT-OS-UBUNTU-2204-CVE-2025-40315, ROOT-OS-UBUNTU-2404-CVE-2025-40315, UBUNTU-CVE-2025-40315

## What is CVE-2025-40315?

CVE-2025-40315 is a vulnerability in Linux, published on 8 Dec 2025. 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 epfile null pointer access after ep enable.

A race condition occurs when ffs_func_eps_enable() runs concurrently
with ffs_data_reset(). The ffs_data_clear() called in ffs_data_reset()
sets ffs->epfiles to NULL before resetting ffs->eps_count to 0, leading
to a NULL pointer dereference when accessing epfile->ep in
ffs_func_eps_enable() after successful usb_ep_enable().

The ffs->epfiles pointer is set to NULL in both ffs_data_clear() and
ffs_data_close() functions, and its modification is protected by the
spinlock ffs->eps_lock. And the whole ffs_func_eps_enable() function
is also protected by ffs->eps_lock.

Thus, add NULL pointer handling for ffs->epfiles in the
ffs_func_eps_enable() function to fix issues

## Which versions are affected by CVE-2025-40315?


## How do I fix CVE-2025-40315?

Apply the vendor's patch.

## Is CVE-2025-40315 being exploited?

There is no known exploitation of CVE-2025-40315 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40315 and fix it if it is affected.

What it is: CVE-2025-40315 is a vulnerability in Linux, published on 8 Dec 2025. 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-2025-40315 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-2025-40315/ (Markdown: https://insights.sbomify.com/CVE-2025-40315/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40315
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40315
- OSV: https://osv.dev/vulnerability/CVE-2025-40315

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40315/
Summaries are generated and may contain mistakes; the official description above is the record.