Linux Kernel IPv6 Checksum GSO Fallback Vulnerability

Publication date: 2026-05-01

Last updated on: 2026-05-06

Assigner: kernel.org

Description

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.

CVSS Scores

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Meta Information

Published

2026-05-01

Last Modified

2026-05-06

Generated

2026-07-06

AI Q&A

2026-05-01

EPSS Evaluated

2026-07-05

NVD

CVE-2026-43057

EUVD

EUVD-2026-26656

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	6.17
linux	linux_kernel	6.17
linux	linux_kernel	6.17
linux	linux_kernel	6.17
linux	linux_kernel	6.17
linux	linux_kernel	6.17
linux	linux_kernel	7.0
linux	linux_kernel	7.0
linux	linux_kernel	7.0
linux	linux_kernel	7.0
linux	linux_kernel	7.0
linux	linux_kernel	From 6.19 (inc) to 6.19.12 (exc)
linux	linux_kernel	From 6.1.149 (inc) to 6.1.168 (exc)
linux	linux_kernel	From 6.12.44 (inc) to 6.12.81 (exc)
linux	linux_kernel	From 6.16.4 (inc) to 6.17 (exc)
linux	linux_kernel	From 6.6.103 (inc) to 6.6.134 (exc)
linux	linux_kernel	From 6.17.1 (exc) to 6.18.22 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability relates to how the Linux kernel handles tunneled IPv6 traffic with checksum offloading and segmentation offloading features. Specifically, the kernel did not correctly handle packets with IPv6 extension headers during checksum offload, which requires software fallback for such packets. The issue was that the kernel only checked the outer network header length, but for tunneled packets, it must check the inner header length instead. Additionally, special cases like tunneled packets without an inner IP protocol (e.g., RFC 6951 SCTP in UDP) were not properly handled and needed to revert to software processing. The vulnerability was fixed by introducing a fallback mechanism that correctly checks the inner header length and ensures proper software handling of these special tunneled packets.

Impact Analysis

If this vulnerability is present, tunneled IPv6 packets with extension headers or special inner protocols might not be processed correctly by the kernel's checksum and segmentation offloading mechanisms. This could lead to incorrect packet handling, potentially causing network communication issues such as dropped or corrupted packets, degraded network performance, or unexpected behavior in applications relying on tunneled IPv6 traffic.

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