# CVE-2026-72117: can: bcm: fix data race on rx_stamp/rx_ifindex in bcm_rx_handler()

> A data race in the Linux kernel CAN BCM handler allows concurrent writes to timestamp fields, potentially causing torn reads or inconsistent state for local attackers.

- **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:** 15 Aug 2026
- **Updated:** 19 Aug 2026
- **Also known as:** BELL-CVE-2026-72117, DEBIAN-CVE-2026-72117, GHSA-rcrc-h682-pmgg, UBUNTU-CVE-2026-72117

## What is CVE-2026-72117?

CVE-2026-72117 is a vulnerability in Linux, published on 15 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:

can: bcm: fix data race on rx_stamp/rx_ifindex in bcm_rx_handler()

For an rx op subscribed on all interfaces (ifindex == 0), the same op
is registered once in the shared per-netns wildcard filter list, so
bcm_rx_handler() can run concurrently on different CPUs for frames
arriving on different net devices.

op->rx_stamp and op->rx_ifindex were written before bcm_rx_update_lock was
taken, allowing concurrent writers to race each other - including a torn
store of the 64-bit rx_stamp on 32-bit platforms.

Beyond a torn store bcm_send_to_user() must report the timestamp/ifindex
of the very same frame whose content it is delivering. So the assignment
is placed in the same unbroken bcm_rx_update_lock section as the content
comparison.

As a side effect, the RTR-request frame feature (which never reach
bcm_send_to_user()) no longer updates rx_stamp/rx_ifindex, since only
the notification path needs them.

## Which versions are affected by CVE-2026-72117?


## How do I fix CVE-2026-72117?

Apply the vendor's patch.

## Is CVE-2026-72117 being exploited?

There is no known exploitation of CVE-2026-72117 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72117 and fix it if it is affected.

What it is: CVE-2026-72117 is a vulnerability in Linux, published on 15 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-2026-72117 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-2026-72117/ (Markdown: https://insights.sbomify.com/CVE-2026-72117/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72117
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72117
- OSV: https://osv.dev/vulnerability/CVE-2026-72117

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72117/
Summaries are generated and may contain mistakes; the official description above is the record.