---
id: CVE-2026-43057
title: 'net: correctly handle tunneled traffic on IPV6_CSUM GSO fallback'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: correctly handle tunneled traffic on IPV6_CSUM GSO fallback

  NETIF_F_IPV6_CSUM only advertises support for checksum offload of
  packets without IPv6 extension heade…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= a0478d7e888028f85fa7785ea838ce0ca09398e2 <
    2094a7cf91b71367b649f991aacc7b579f793d0b
  - >-
    Linux >= 2156d9e9f2e483c8c3906c0ea57ea312c1424235 <
    ed71cf465c75f5688b07a35d373cd1d6b589c8ea
  - >-
    Linux >= 041e2f945f82fdbd6fff577b79c33469430297aa <
    33670f780e0120c3dacda188c512bbffe0b6044c
  - >-
    Linux >= 864e3396976ef41de6cc7bc366276bf4e084fff2 <
    a98b78116a27e2a57b696b569b2cb431c95cf9b6
  - >-
    Linux >= 864e3396976ef41de6cc7bc366276bf4e084fff2 <
    732fdeb2987c94b439d51f5cb9addddc2fc48c42
  - >-
    Linux >= 864e3396976ef41de6cc7bc366276bf4e084fff2 <
    c4336a07eb6b2526dc2b62928b5104b41a7f81f5
  - Linux 794ddbb7b63b6828c75967b9bcd43b086716e7a1
  - Linux >= 6.1.149 < 6.1.168
  - Linux >= 6.6.103 < 6.6.134
  - Linux >= 6.12.44 < 6.12.81
  - Linux >= 6.16.4 < 6.17
  - Linux 6.17
published: '2026-05-01'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T08:48:43.313Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-43057'
references:
  - url: 'https://git.kernel.org/stable/c/2094a7cf91b71367b649f991aacc7b579f793d0b'
  - url: 'https://git.kernel.org/stable/c/ed71cf465c75f5688b07a35d373cd1d6b589c8ea'
  - url: 'https://git.kernel.org/stable/c/33670f780e0120c3dacda188c512bbffe0b6044c'
  - url: 'https://git.kernel.org/stable/c/a98b78116a27e2a57b696b569b2cb431c95cf9b6'
  - url: 'https://git.kernel.org/stable/c/732fdeb2987c94b439d51f5cb9addddc2fc48c42'
  - url: 'https://git.kernel.org/stable/c/c4336a07eb6b2526dc2b62928b5104b41a7f81f5'
tags:
  - cve.org
epss: 0.00716
epssPercentile: 0.51714
ingestedAt: '2026-09-08T15:33:26.989Z'
---

## Overview

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

net: correctly handle tunneled traffic on IPV6_CSUM GSO fallback

NETIF_F_IPV6_CSUM only advertises support for checksum offload of
packets without IPv6 extension headers. Packets with extension
headers must fall back onto software checksumming. Since TSO
depends on checksum offload, those must revert to GSO.

The below commit introduces that fallback. It always checks
network header length. For tunneled packets, the inner header length
must be checked instead. Extend the check accordingly.

A special case is tunneled packets without inner IP protocol. Such as
RFC 6951 SCTP in UDP. Those are not standard IPv6 followed by
transport header either, so also must revert to the software GSO path.

## Affected

- `Linux >= a0478d7e888028f85fa7785ea838ce0ca09398e2 < 2094a7cf91b71367b649f991aacc7b579f793d0b`
- `Linux >= 2156d9e9f2e483c8c3906c0ea57ea312c1424235 < ed71cf465c75f5688b07a35d373cd1d6b589c8ea`
- `Linux >= 041e2f945f82fdbd6fff577b79c33469430297aa < 33670f780e0120c3dacda188c512bbffe0b6044c`
- `Linux >= 864e3396976ef41de6cc7bc366276bf4e084fff2 < a98b78116a27e2a57b696b569b2cb431c95cf9b6`
- `Linux >= 864e3396976ef41de6cc7bc366276bf4e084fff2 < 732fdeb2987c94b439d51f5cb9addddc2fc48c42`
- `Linux >= 864e3396976ef41de6cc7bc366276bf4e084fff2 < c4336a07eb6b2526dc2b62928b5104b41a7f81f5`
- `Linux 794ddbb7b63b6828c75967b9bcd43b086716e7a1`
- `Linux >= 6.1.149 < 6.1.168`
- `Linux >= 6.6.103 < 6.6.134`
- `Linux >= 6.12.44 < 6.12.81`
- `Linux >= 6.16.4 < 6.17`
- `Linux 6.17`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.