# CVE-2026-98301: net: bridge: mst: move switchdev call outside rcu

> A sleeping function called from invalid context in the Linux kernel bridge MST code can cause a system crash or denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-106266, BELL-CVE-2026-98301, DEBIAN-CVE-2026-98301, GHSA-rcgj-3ccr-mx7g, UBUNTU-CVE-2026-98301

## What is CVE-2026-98301?

CVE-2026-98301 is a denial of service vulnerability in Linux, published on 6 Oct 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: bridge: mst: move switchdev call outside rcu

This is a follow-up of one of sashiko's pre-existing bug reports.
br_mst_set_state() calls switchdev_port_attr_set() for nonzero MSTIs
while holding rcu_read_lock() which invokes the blocking switchdev
notifier chain and may sleep. Nonzero MSTI changes come from netlink
with rtnl held. Move the switchdev call before entering the rcu section and
assert that rtnl is held.

The call cannot be deferred because netlink needs its error and extack.
Also DSA reads the old bridge MST state during the callback and checks it.
A deferred callback will be late and will see the updated state.

## Which versions are affected by CVE-2026-98301?


## How do I fix CVE-2026-98301?

Apply the vendor's patch.

## Is CVE-2026-98301 being exploited?

There is no known exploitation of CVE-2026-98301 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98301 and fix it if it is affected.

What it is: CVE-2026-98301 is a denial of service vulnerability in Linux, published on 6 Oct 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-2026-98301 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-2026-98301/ (Markdown: https://insights.sbomify.com/CVE-2026-98301/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98301
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98301
- OSV: https://osv.dev/vulnerability/CVE-2026-98301

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98301/
Summaries are generated and may contain mistakes; the official description above is the record.