---
id: CVE-2026-89661
title: >-
  kernel: NFSD: Prevent post-shutdown use-after-free in unlock_filesystem
  (CVE-2026-89661)
summary: >-
  A flaw was found in the Linux kernel's Network File System Daemon (NFSD). A
  local administrator with CAP_SYS_ADMIN capabilities can trigger a
  use-after-free vulnerability by writing to /proc/fs/nfsd/unlock_filesystem
  after the NFSD server …
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-825
vendor: Red Hat
product: Red Hat Enterprise Linux 10
affected:
  - enterprise_linux 10
  - enterprise_linux 6
published: '2026-09-11'
updated: '2026-09-16'
sourceUpdated: '2026-09-16T05:50:10+00:00'
source: CSAF
sourceUrl: 'https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89661.json'
references:
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89661.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89661'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532346'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89661'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89661'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89661.mbox
  - url: 'https://git.kernel.org/stable/c/0c1a755b7212e0835398d4df5e782ea85ccd7476'
  - url: 'https://git.kernel.org/stable/c/292d915d3ba6fd15eeb88351fa10581683073109'
tags:
  - csaf
  - vex
  - red-hat
  - cve.org
epss: 0.00198
epssPercentile: 0.08439
ingestedAt: '2026-09-14T11:11:19.886Z'
---

## Overview

A flaw was found in the Linux kernel's Network File System Daemon (NFSD). A local administrator with CAP_SYS_ADMIN capabilities can trigger a use-after-free vulnerability by writing to /proc/fs/nfsd/unlock_filesystem after the NFSD server has shut down. This can lead to memory corruption, potentially causing a denial of service.

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 10 · updated 2026-09-16 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89661.json)

**kernel: NFSD: Prevent post-shutdown use-after-free in unlock_filesystem** — rated Moderate by Red Hat. Released 2026-09-11, updated 2026-09-16.

Affected:

- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 6

No fix planned:

- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 10

Not affected:

- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
- Red Hat OpenShift Container Platform 4

## Remediation

Out of support scope