# CVE-2026-93204: batman-adv: dat: atomically update mac addresses

> A race condition in the Linux kernel batman-adv module allows attackers to poison ARP caches by exploiting non-atomic MAC address updates.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-103035, BELL-CVE-2026-93204, DEBIAN-CVE-2026-93204, GHSA-9fhg-rrvj-mjc8, UBUNTU-CVE-2026-93204

## What is CVE-2026-93204?

CVE-2026-93204 is a vulnerability in Linux, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

batman-adv: dat: atomically update mac addresses

When a MAC address is updated in batadv_dat_entry_add(), it is done using a
simple copy function. A parallel reader might only see parts of this
update. In worst case, the reader is transporting the half updated MAC
address over the network or is creating an ARP response using it -
poisoning the ARP cache.

atomic64_t can be used to store the 48 bit of a mac address. A reader will
then either see the old mac address or the new one - never a mixture of
both.

## Which versions are affected by CVE-2026-93204?


## How do I fix CVE-2026-93204?

Apply the vendor's patch.

## Is CVE-2026-93204 being exploited?

There is no known exploitation of CVE-2026-93204 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93204 and fix it if it is affected.

What it is: CVE-2026-93204 is a vulnerability in Linux, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-93204 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-2026-93204/ (Markdown: https://insights.sbomify.com/CVE-2026-93204/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93204
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93204
- OSV: https://osv.dev/vulnerability/CVE-2026-93204

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93204/
Summaries are generated and may contain mistakes; the official description above is the record.