---
id: CVE-2026-68123
title: 'openvswitch: fix GSO userspace truncation underflow'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  openvswitch: fix GSO userspace truncation underflow

  OVS_ACTION_ATTR_TRUNC currently stores a delta from the original skb
  length in OVS_CB(skb)->cutlen. When a later us…
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 <
    50a6a85f3d6b1d22d8436848606cdef5d2c490b4
  - >-
    Linux >= f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 <
    2623c48cc3a8da9a1886fd8f65c0e348f4406fd6
  - >-
    Linux >= f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 <
    e211b081901ffca76674082c73eeaed53524c369
  - >-
    Linux >= f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 <
    a16eaaf7c0b0ccdef6166707d90ffbc6eebf6855
  - >-
    Linux >= f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 <
    fbfa3ad2ad6f3a5624aba5211c46290fb98cc9dc
  - >-
    Linux >= f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 <
    100a23b1613e9218e0af654ef102352c713f0263
  - >-
    Linux >= f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 <
    ea85dbcbe8d4056ecb54352f97743d138ea4c407
  - >-
    Linux >= f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 <
    4032f8ed10fcb84d41c508dfb04be96589f78dfe
  - Linux 4.8
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-10-16T15:44:13.520896Z'
published: '2026-08-10'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T15:52:57.977Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-68123'
references:
  - url: 'https://git.kernel.org/stable/c/50a6a85f3d6b1d22d8436848606cdef5d2c490b4'
  - url: 'https://git.kernel.org/stable/c/2623c48cc3a8da9a1886fd8f65c0e348f4406fd6'
  - url: 'https://git.kernel.org/stable/c/e211b081901ffca76674082c73eeaed53524c369'
  - url: 'https://git.kernel.org/stable/c/a16eaaf7c0b0ccdef6166707d90ffbc6eebf6855'
  - url: 'https://git.kernel.org/stable/c/fbfa3ad2ad6f3a5624aba5211c46290fb98cc9dc'
  - url: 'https://git.kernel.org/stable/c/100a23b1613e9218e0af654ef102352c713f0263'
  - url: 'https://git.kernel.org/stable/c/ea85dbcbe8d4056ecb54352f97743d138ea4c407'
  - url: 'https://git.kernel.org/stable/c/4032f8ed10fcb84d41c508dfb04be96589f78dfe'
tags:
  - cve.org
epss: 0.00552
epssPercentile: 0.44907
ingestedAt: '2026-10-16T17:24:46.842Z'
---

## Overview

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

openvswitch: fix GSO userspace truncation underflow

OVS_ACTION_ATTR_TRUNC currently stores a delta from the original skb
length in OVS_CB(skb)->cutlen. When a later userspace action segments a
GSO skb, queue_gso_packets() reuses that delta for each smaller segment.
A segment can then reach queue_userspace_packet() with cutlen greater
than skb->len, underflowing the length passed to skb_zerocopy().

Store the maximum preserved length instead and bound each consumer
against the current skb length. Use U32_MAX as the no-truncation
sentinel so the value remains valid if skb geometry changes before a
consumer handles it.

## Affected

- `Linux >= f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 < 50a6a85f3d6b1d22d8436848606cdef5d2c490b4`
- `Linux >= f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 < 2623c48cc3a8da9a1886fd8f65c0e348f4406fd6`
- `Linux >= f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 < e211b081901ffca76674082c73eeaed53524c369`
- `Linux >= f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 < a16eaaf7c0b0ccdef6166707d90ffbc6eebf6855`
- `Linux >= f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 < fbfa3ad2ad6f3a5624aba5211c46290fb98cc9dc`
- `Linux >= f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 < 100a23b1613e9218e0af654ef102352c713f0263`
- `Linux >= f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 < ea85dbcbe8d4056ecb54352f97743d138ea4c407`
- `Linux >= f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 < 4032f8ed10fcb84d41c508dfb04be96589f78dfe`
- `Linux 4.8`

## Remediation

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