# CVE-2026-68217: media: pwc: Drain fill_buf on start_streaming() failure

> A race condition in the Linux kernel pwc driver leaks a buffer on streaming failure, potentially causing a kernel warning and denial of service.

- **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:** 10 Aug 2026
- **Updated:** 19 Aug 2026
- **Also known as:** BELL-CVE-2026-68217, DEBIAN-CVE-2026-68217, GHSA-mj4m-5r47-3f8j, UBUNTU-CVE-2026-68217

## What is CVE-2026-68217?

CVE-2026-68217 is a memory corruption vulnerability in Linux, published on 10 Aug 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:

media: pwc: Drain fill_buf on start_streaming() failure

pwc_isoc_init() submits its isochronous URBs with
usb_submit_urb(.., GFP_KERNEL) in a loop. After the first URB is
submitted, its completion handler pwc_isoc_handler() can run on another
CPU before the loop finishes:

  start_streaming()
    pwc_isoc_init()
      usb_submit_urb(urbs[0], GFP_KERNEL)
                                  pwc_isoc_handler(urbs[0])
                                    pdev->fill_buf =
                                      pwc_get_next_fill_buf(pdev)
      usb_submit_urb(urbs[i>0], ..)  -> fails
      pwc_isoc_cleanup(pdev)           /* kills URBs */
      return ret;
    pwc_cleanup_queued_bufs(pdev, VB2_BUF_STATE_QUEUED)

pwc_get_next_fill_buf() detaches a buffer from pdev->queued_bufs and
stores it in pdev->fill_buf. The error path in start_streaming() only
drains pdev->queued_bufs, so the buffer parked in pdev->fill_buf is
leaked. vb2_start_streaming() then triggers
WARN_ON(owned_by_drv_count).

stop_streaming() already handles this since commit 80b0963e1698
("[media] pwc: fix WARN_ON"), which added the fill_buf drain in the
teardown path but not in the start_streaming() error path. Mirror that
handling on failure so start_streaming() returns with no buffer owned
by the driver.

Issue identified by automated review of the INV-003 series at
https://sashiko.dev/

## Which versions are affected by CVE-2026-68217?


## How do I fix CVE-2026-68217?

Apply the vendor's patch.

## Is CVE-2026-68217 being exploited?

There is no known exploitation of CVE-2026-68217 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-68217 and fix it if it is affected.

What it is: CVE-2026-68217 is a memory corruption vulnerability in Linux, published on 10 Aug 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-2026-68217 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-2026-68217/ (Markdown: https://insights.sbomify.com/CVE-2026-68217/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-68217
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-68217
- OSV: https://osv.dev/vulnerability/CVE-2026-68217

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-68217/
Summaries are generated and may contain mistakes; the official description above is the record.