---
id: CVE-2026-31685
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  netfilter: ip6t_eui64: reject invalid MAC header for all packets

  `eui64_mt6()` derives a modified EUI-64 from the Ethernet source address
  and compares it with the low …
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  netfilter: ip6t_eui64: reject invalid MAC header for all packets

  `eui64_mt6()` derives a modified EUI-64 from the Ethernet source address
  and compares it with the low …
severity: critical
cvss: 9.4
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:H'
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 2.6.12.1, < 6.6.136'
  - 'linux_kernel >= 6.7, < 6.12.83'
  - 'linux_kernel >= 6.13, < 6.18.24'
  - 'linux_kernel >= 6.19, < 6.19.14'
  - linux_kernel = 2.6.12
  - linux_kernel = 7.0
patched:
  - linux_kernel 6.19.14
published: '2026-04-25'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T02:19:17.423'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-31685'
references:
  - url: 'https://git.kernel.org/stable/c/288138418bef956f8b295751a4536c60f0e89f4a'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/309ae3e9a51a69699ca94eac5fac5688fa562d55'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/4d75bc2cd093bf5803edf512c099bfb220fd6459'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7d6a57411caf54df025860c9b1a82cd42d57a562'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/807d6ee15804df6f01a35c910f09612e858739a6'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/9eda5478746ef7dc0e4e537b5a5e4b0ca1027091'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/d5603591373441fecf9951833d6d873e09320f08'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/fdce0b3590f724540795b874b4c8850c90e6b0a8'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-784472.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - cve.org
epss: 0.00337
epssPercentile: 0.25488
ingestedAt: '2026-10-15T03:30:12.864Z'
---

## Overview

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

netfilter: ip6t_eui64: reject invalid MAC header for all packets

`eui64_mt6()` derives a modified EUI-64 from the Ethernet source address
and compares it with the low 64 bits of the IPv6 source address.

The existing guard only rejects an invalid MAC header when
`par->fragoff != 0`. For packets with `par->fragoff == 0`, `eui64_mt6()`
can still reach `eth_hdr(skb)` even when the MAC header is not valid.

Fix this by removing the `par->fragoff != 0` condition so that packets
with an invalid MAC header are rejected before accessing `eth_hdr(skb)`.

## Affected

- `linux_kernel >= 2.6.12.1, < 6.6.136`
- `linux_kernel >= 6.7, < 6.12.83`
- `linux_kernel >= 6.13, < 6.18.24`
- `linux_kernel >= 6.19, < 6.19.14`
- `linux_kernel = 2.6.12`
- `linux_kernel = 7.0`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.19.14`