---
id: "CVE-2026-98568"
kind: "vulnerability"
aliases: ["CVE-2026-98568"]
title: "Linux kernel: VXLAN neighbour reply race writes past skb buffer"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["kubernetes", "linux-kernel", "runtime", "self-hosted", "vxlan"]
not_affected_if: ["default-config", "no-vxlan"]
published_at: "2026-10-18T16:17:09+00:00"
first_seen_at: "2026-10-23T21:57:15+00:00"
updated_at: "2026-10-25T05:23:15+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98568", "first_seen_at": "2026-10-23T21:57:15+00:00"}]
---

# Linux kernel: VXLAN neighbour reply race writes past skb buffer

A race in the Linux kernel's VXLAN driver lets a concurrent link change make the neighbour-reply code size its buffer too small. The result is an out-of-bounds write of a few bytes into kernel memory, which can corrupt the kernel.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- unknown

## Fix

- Update to a Linux kernel release that includes the upstream commit using one headroom snapshot in vxlan_na_create() (the fix named in the advisory); exact fixed version unknown from the sources.

## Timeline

- 2026-10-23T21:57:15+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98568

## From the sources

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.

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