---
id: CVE-2026-89704
title: >-
  kernel: nfsd: sample writeback error cursor before async COPY loop
  (CVE-2026-89704)
summary: >-
  A flaw was found in the Linux kernel's nfsd component. The
  _nfsd_copy_file_range() function incorrectly samples the writeback error
  cursor after the copy loop. This allows a concurrent write operation to
  advance the error cursor prematurel…
severity: high
cvss: 7
cvssVector: 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: vendor
cwe: CWE-367
vendor: Red Hat
product: Red Hat Enterprise Linux 9
affected:
  - enterprise_linux 10
  - enterprise_linux 6
  - enterprise_linux 9
  - openshift_container_platform 4
published: '2026-09-11'
updated: '2026-09-21'
sourceUpdated: '2026-09-21T14:17:30+00:00'
source: CSAF
sourceUrl: 'https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89704.json'
references:
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89704.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89704'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532298'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89704'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89704'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89704.mbox
  - url: 'https://git.kernel.org/stable/c/435e4246c7dfff2fbd76dfdbf91975d5d9f788c9'
  - url: 'https://git.kernel.org/stable/c/9f539a1c0791f907eb4e6d04b43178d9962e2def'
  - url: 'https://git.kernel.org/stable/c/4728504c021656128a07f4693af80ed4a5fcc863'
  - url: 'https://git.kernel.org/stable/c/322422d66d1a04434a0dcc0c9d3a4c4b3f225117'
  - url: 'https://git.kernel.org/stable/c/52b2db7a72e19ac2686fa4b2a52406661e7bf9e2'
  - url: 'https://git.kernel.org/stable/c/8277d4a11ae2cb5495842be558fd946032c24363'
  - url: 'https://git.kernel.org/stable/c/a1cbafe756cd5e6ab0e099062f37da7a5b081169'
  - url: 'https://git.kernel.org/stable/c/20a67a7d18221af736f124770c2c5e859b479046'
tags:
  - csaf
  - vex
  - red-hat
  - cve.org
epss: 0.00511
epssPercentile: 0.42618
scores:
  vendor: 7
  cna: 7.5
ingestedAt: '2026-09-14T15:23:07.449Z'
---

## Overview

A flaw was found in the Linux kernel's nfsd component. The _nfsd_copy_file_range() function incorrectly samples the writeback error cursor after the copy loop. This allows a concurrent write operation to advance the error cursor prematurely. As a result, the system may report that data has been successfully committed even when writeback errors have occurred, leading to silent data loss where clients perceive data as durable when it is not.

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 10, 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-2026-89704.json)

**kernel: nfsd: sample writeback error cursor before async COPY loop** — rated Moderate by Red Hat. Released 2026-09-11, updated 2026-09-21.

Affected:

- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 9
- Red Hat OpenShift Container Platform 4

No fix planned:

- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 9
- Red Hat OpenShift Container Platform 4

Not affected:

- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8
- Red Hat OpenShift Container Platform 4

## Remediation

Out of support scope