# CVE-2026-98026: net: bridge: mcast: properly convert mglist to rcu

> A use-after-free vulnerability in the Linux kernel bridge multicast code allows local attackers to cause a denial of service or potentially execute code.

- **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:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-104513, BELL-CVE-2026-98026, DEBIAN-CVE-2026-98026, GHSA-r366-wr25-m9fj, UBUNTU-CVE-2026-98026

## What is CVE-2026-98026?

CVE-2026-98026 is an use after free vulnerability in Linux, published on 25 Sep 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: mcast: properly convert mglist to rcu

Sashiko reported a bug [1] that br_multicast_del_port_group unlists the
port group not using proper rcu helper that preserves the next pointer and
after that immediately frees the port group without waiting for rcu grace
period. The only rcu walker of mglist is br_multicast_list_adjacent() and
it turns out that function has always been buggy because mglist was never
properly converted to RCU. Fix it by converting it to rcu and moving its
initialization after eth_addr's. Initializing p->next can use
RCU_INIT_POINTER because we have a barrier from the hlist_add_head_rcu call
later, besides we're initializing an unpublished structure anyway.

[1] https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260826014200.362304-1-littleddfu%40gmail.com

## Which versions are affected by CVE-2026-98026?


## How do I fix CVE-2026-98026?

Apply the vendor's patch.

## Is CVE-2026-98026 being exploited?

There is no known exploitation of CVE-2026-98026 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98026 and fix it if it is affected.

What it is: CVE-2026-98026 is an use after free vulnerability in Linux, published on 25 Sep 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-2026-98026 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-2026-98026/ (Markdown: https://insights.sbomify.com/CVE-2026-98026/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98026
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98026
- OSV: https://osv.dev/vulnerability/CVE-2026-98026

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98026/
Summaries are generated and may contain mistakes; the official description above is the record.