# CVE-2026-72340: net: microchip: vcap: fix races on the shared Super VCAP block

> A race condition in the Linux kernel's Microchip VCAP driver allows concurrent access to corrupt hardware entries, potentially causing data corruption or denial of service.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-72340, DEBIAN-CVE-2026-72340, GHSA-57m3-p558-ghpc, UBUNTU-CVE-2026-72340

## What is CVE-2026-72340?

CVE-2026-72340 is a high-severity 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:

net: microchip: vcap: fix races on the shared Super VCAP block

The VCAP instances on a chip are not independent, yet they are locked
independently. On sparx5 and lan969x the IS0 and IS2 instances are
backed by the same Super VCAP hardware block and share its cache and
command registers: every access drives the shared VCAP_SUPER_CTRL
register and moves data through the shared cache registers.

Accessing one instance therefore races with accessing another. The
per-instance admin->lock cannot prevent this, as each instance takes a
different lock.

The locking issue is mostly disguised by the fact that the core usage of
the vcap api runs under rtnl. However, the full rule dump in debugfs
decodes rules straight from hardware (a READ command followed by a cache
read) and runs outside rtnl, so it races a concurrent tc-flower rule
write to another Super VCAP instance.

Besides corrupting the dump, the read repopulates the shared cache
between the writers cache fill and its write command, so the writer
commits the wrong data and corrupts the hardware entry.

Introduce vcap_lock() and vcap_unlock() helpers and route every rule
lock site in the VCAP API and its debugfs code through them. Replace the
per-instance admin->lock with a single mutex in struct vcap_control that
serializes access to all instances. The helpers reach it through a new
admin->vctrl back-pointer, and the clients initialise and destroy the
control lock instead of a per-instance one.

No path holds more than one instance lock, so collapsing them onto a
single mutex cannot self-deadlock.

## Which versions are affected by CVE-2026-72340?


## How do I fix CVE-2026-72340?

Apply the vendor's patch.

## Is CVE-2026-72340 being exploited?

There is no known exploitation of CVE-2026-72340 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72340 and fix it if it is affected.

What it is: CVE-2026-72340 is a high-severity 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-2026-72340 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-2026-72340/ (Markdown: https://insights.sbomify.com/CVE-2026-72340/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72340
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72340
- OSV: https://osv.dev/vulnerability/CVE-2026-72340

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72340/
Summaries are generated and may contain mistakes; the official description above is the record.