# CVE-2026-98347: IB/IPoIB: Avoid restoring OPER_UP after multicast flush

> A race condition in the Linux kernel IPoIB driver can cause a deadlock during interface shutdown, leading to a 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:** 6 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-106446, BELL-CVE-2026-98347, DEBIAN-CVE-2026-98347, GHSA-8j4r-887v-cjjx, UBUNTU-CVE-2026-98347

## What is CVE-2026-98347?

CVE-2026-98347 is a 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:

IB/IPoIB: Avoid restoring OPER_UP after multicast flush

ipoib_ib_dev_flush_light() temporarily clears IPOIB_FLAG_OPER_UP to
prevent multicast joins while ipoib_mcast_dev_flush() is running, and
restores the flag afterwards if it was previously set.

This restore races with ipoib_ib_dev_down(). If the interface is brought
down while the flush is in progress, ipoib_ib_dev_down() clears
IPOIB_FLAG_OPER_UP, but the flush path may set it again after the device
has already gone down.

Since commit 894021a75291 ("IB/ipoib: Make the carrier_on_task race
aware"), ipoib_mcast_carrier_on_task() relies on IPOIB_FLAG_OPER_UP
being cleared to terminate its rtnl_trylock() retry loop. If the flag is
left set after shutdown, the workqueue retries forever, causing teardown
to deadlock when ipoib_ndo_uninit() waits in destroy_workqueue() while
holding RTNL.

Instead of overloading IPOIB_FLAG_OPER_UP to block multicast joins
during a light flush, introduce a dedicated IPOIB_FLAG_MCAST_FLUSH flag.
Use it together with IPOIB_FLAG_OPER_UP to determine whether multicast
joins are allowed, avoiding the race with device shutdown.

## Which versions are affected by CVE-2026-98347?


## How do I fix CVE-2026-98347?

Apply the vendor's patch.

## Is CVE-2026-98347 being exploited?

There is no known exploitation of CVE-2026-98347 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98347 and fix it if it is affected.

What it is: CVE-2026-98347 is a 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-2026-98347 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-2026-98347/ (Markdown: https://insights.sbomify.com/CVE-2026-98347/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98347
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98347
- OSV: https://osv.dev/vulnerability/CVE-2026-98347

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98347/
Summaries are generated and may contain mistakes; the official description above is the record.