# CVE-2026-98568: vxlan: use one headroom snapshot for neighbour replies

> A race condition in the Linux kernel VXLAN module allows out-of-bounds writes during neighbour reply generation, potentially leading to code execution 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:** 18 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-109263, BELL-CVE-2026-98568, DEBIAN-CVE-2026-98568, GHSA-489c-q3cc-mm5r, UBUNTU-CVE-2026-98568

## What is CVE-2026-98568?

CVE-2026-98568 is a vulnerability in Linux, published on 18 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:

vxlan: use one headroom snapshot for neighbour replies

vxlan_na_create() samples LL_RESERVED_SPACE() to size the reply skb and then
samples it again to reserve headroom. A concurrent vxlan_changelink() can
update needed_headroom between the two reads, creating a TOCTOU race. The
second value can exceed the allocation and make the Ethernet header write out
of bounds.

The race is reproducible on the unpatched kernel. It occurred when
vxlan_na_create() generated a neighbour reply while vxlan_changelink() changed
the link headroom. KASAN caught a four-byte write two bytes beyond a 704-byte
skbuff_small_head allocation.

Snapshot the headroom once and use that value for both allocation and
reservation.

## Which versions are affected by CVE-2026-98568?


## How do I fix CVE-2026-98568?

Apply the vendor's patch.

## Is CVE-2026-98568 being exploited?

There is no known exploitation of CVE-2026-98568 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98568 and fix it if it is affected.

What it is: CVE-2026-98568 is a vulnerability in Linux, published on 18 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-2026-98568 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-2026-98568/ (Markdown: https://insights.sbomify.com/CVE-2026-98568/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98568
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98568
- OSV: https://osv.dev/vulnerability/CVE-2026-98568

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98568/
Summaries are generated and may contain mistakes; the official description above is the record.