---
id: CVE-2026-89659
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  NFSD: Prevent client use-after-free during delegation revoke

  A delegation stateid holds only a bare pointer to its owning
  nfs4_client and does not keep it alive
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  NFSD: Prevent client use-after-free during delegation revoke

  A delegation stateid holds only a bare pointer to its owning
  nfs4_client and does not keep it alive.  The …
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'
cwe:
  - CWE-825
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54 <
    0dd276b1324a5e08e83c6f675919946c9f0d61c9
  - >-
    Linux >= 3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54 <
    3c0a53ee0b442348d8d2286d6960d3f07bb3a3d3
  - >-
    Linux >= 3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54 <
    2a9d637c2a8fd8ac29ad9b29f28d122ef75c1a56
  - >-
    Linux >= 3bd64a5ba1719c2bb6cba4493dfd3e23a7653e54 <
    4683ca76b3b7e5808338491c6eb3c20e6b4894d5
  - Linux 3.10
published: '2026-09-11'
updated: '2026-09-21'
sourceUpdated: '2026-09-21T14:17:24.513'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89659'
references:
  - url: 'https://git.kernel.org/stable/c/0dd276b1324a5e08e83c6f675919946c9f0d61c9'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/2a9d637c2a8fd8ac29ad9b29f28d122ef75c1a56'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/3c0a53ee0b442348d8d2286d6960d3f07bb3a3d3'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/4683ca76b3b7e5808338491c6eb3c20e6b4894d5'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89659.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89659'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532119'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89659'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89659'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89659.mbox
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
  - score-dispute
epss: 0.00652
epssPercentile: 0.49031
scores:
  nvd: 9.8
  cna: 9.8
  vendor: 7
ingestedAt: '2026-09-14T15:23:07.473Z'
---

## Overview

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

NFSD: Prevent client use-after-free during delegation revoke

A delegation stateid holds only a bare pointer to its owning
nfs4_client and does not keep it alive.  The client survives its
stateids only because __destroy_client() drains cl_delegations and
cl_revoked before free_client() runs.

nfs4_laundromat() breaks that invariant: it unhashes an
expired delegation from cl_delegations, drops deleg_lock, then
revoke_delegation() relinks it onto cl_revoked under cl_lock.  In that
window the delegation is on neither list, so client_has_state() can
report no remaining state.

Every teardown path first requires cl_rpc_users to be zero, but
the laundromat holds no such reference.  A client whose recalled
delegation has just timed out can therefore reach free_client()
while revoke_delegation() is still about to dereference cl_lock,
a use-after-free.

Pin the client with cl_rpc_users across the revoke so teardown blocks
until it completes, then reap the delegation from cl_revoked.  A client
already expiring reaps its own, so skip it and leave the delegation on
del_recall_lru.

## Remediation

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

## Vendor advisories

- **Red Hat VEX** · Important · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4, Red Hat Enterprise Linux 6 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, … · updated 2026-09-15 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89659.json)