# CVE-2025-68339: atm/fore200e: Fix possible data race in fore200e_open()

> A race condition in the Linux kernel ATM fore200e driver allows concurrent access to shared bandwidth resources, potentially causing incorrect accounting and denial of service.

- **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:** 23 Dec 2025
- **Updated:** 11 May 2026
- **Also known as:** AZL-72980, BELL-CVE-2025-68339, DEBIAN-CVE-2025-68339, GHSA-p5pr-v4m5-r2vj, ROOT-OS-DEBIAN-12-CVE-2025-68339, ROOT-OS-DEBIAN-13-CVE-2025-68339, ROOT-OS-UBUNTU-2204-CVE-2025-68339, ROOT-OS-UBUNTU-2404-CVE-2025-68339, UBUNTU-CVE-2025-68339

## What is CVE-2025-68339?

CVE-2025-68339 is a vulnerability in Linux, published on 23 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:

atm/fore200e: Fix possible data race in fore200e_open()

Protect access to fore200e->available_cell_rate with rate_mtx lock in the
error handling path of fore200e_open() to prevent a data race.

The field fore200e->available_cell_rate is a shared resource used to track
available bandwidth. It is concurrently accessed by fore200e_open(),
fore200e_close(), and fore200e_change_qos().

In fore200e_open(), the lock rate_mtx is correctly held when subtracting
vcc->qos.txtp.max_pcr from available_cell_rate to reserve bandwidth.
However, if the subsequent call to fore200e_activate_vcin() fails, the
function restores the reserved bandwidth by adding back to
available_cell_rate without holding the lock.

This introduces a race condition because available_cell_rate is a global
device resource shared across all VCCs. If the error path in
fore200e_open() executes concurrently with operations like
fore200e_close() or fore200e_change_qos() on other VCCs, a
read-modify-write race occurs.

Specifically, the error path reads the rate without the lock. If another
CPU acquires the lock and modifies the rate (e.g., releasing bandwidth in
fore200e_close()) between this read and the subsequent write, the error
path will overwrite the concurrent update with a stale value. This results
in incorrect bandwidth accounting.

## Which versions are affected by CVE-2025-68339?


## How do I fix CVE-2025-68339?

Apply the vendor's patch.

## Is CVE-2025-68339 being exploited?

There is no known exploitation of CVE-2025-68339 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-68339 and fix it if it is affected.

What it is: CVE-2025-68339 is a vulnerability in Linux, published on 23 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-2025-68339 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-2025-68339/ (Markdown: https://insights.sbomify.com/CVE-2025-68339/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-68339
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-68339
- OSV: https://osv.dev/vulnerability/CVE-2025-68339

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-68339/
Summaries are generated and may contain mistakes; the official description above is the record.