---
id: CVE-2026-89751
title: 'kernel: x86/tdx: Fix off-by-one in port I/O handling (CVE-2026-89751)'
summary: >-
  A flaw was found in the Linux kernel's x86/tdx component. An off-by-one error
  in the `handle_in()` and `handle_out()` functions, specifically in the
  `GENMASK` calculation for port I/O operations, causes the mask to be one bit
  too wide. Thi…
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cvssSource: vendor
cwe: CWE-193
vendor: Red Hat
product: Red Hat Enterprise Linux 9
affected:
  - enterprise_linux 10
  - enterprise_linux 8
  - enterprise_linux 9
  - openshift_container_platform 4
published: '2026-09-11'
updated: '2026-09-21'
sourceUpdated: '2026-09-21T17:37:47+00:00'
source: CSAF
sourceUrl: 'https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89751.json'
references:
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89751.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89751'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532152'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89751'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89751'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89751.mbox
  - url: 'https://git.kernel.org/stable/c/0f63e656b1c679d32ac595de29d10c03efca6a25'
  - url: 'https://git.kernel.org/stable/c/222b7005e4519f633b4cd666226256abbab46a1a'
  - url: 'https://git.kernel.org/stable/c/bb45f705c4440dd3c689328319b88dd28770bbb8'
  - url: 'https://git.kernel.org/stable/c/c4a22154870813d10aa0b4c734a574c726f9d4b0'
  - url: 'https://git.kernel.org/stable/c/c6875423ad849ac234ab9812eb72f37ff8a490b4'
  - url: 'https://git.kernel.org/stable/c/220011fe95fc78b2bc2d7d43893bc73957a5c811'
tags:
  - csaf
  - vex
  - red-hat
  - cve.org
epss: 0.00172
epssPercentile: 0.06961
ingestedAt: '2026-09-14T15:23:07.448Z'
---

## Overview

A flaw was found in the Linux kernel's x86/tdx component. An off-by-one error in the `handle_in()` and `handle_out()` functions, specifically in the `GENMASK` calculation for port I/O operations, causes the mask to be one bit too wide. This incorrect handling of I/O sizes could potentially lead to unintended data access or modification during port I/O operations, which may result in information disclosure or data corruption.

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · updated 2026-09-21 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89751.json)

**kernel: x86/tdx: Fix off-by-one in port I/O handling** — rated Moderate by Red Hat. Released 2026-09-11, updated 2026-09-21.

Affected:

- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
- Red Hat OpenShift Container Platform 4

No fix planned:

- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
- Red Hat OpenShift Container Platform 4

Not affected:

- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat OpenShift Container Platform 4

## Remediation

Fix deferred