---
id: CVE-2026-90036
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  NFSD: Prevent client use-after-free during blocked-lock reaping

  A bare lock owner -- its only remaining reference a blocked lock on
  nn->blocked_locks_lru -- holds a ra…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  NFSD: Prevent client use-after-free during blocked-lock reaping

  A bare lock owner -- its only remaining reference a blocked lock on
  nn->blocked_locks_lru -- holds a ra…
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'
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 7919d0a27f1e7cb324e023776aa1cbff00f1ee7b <
    cd489b03587378645fe0d20142a33f1ed60bac98
  - >-
    Linux >= 7919d0a27f1e7cb324e023776aa1cbff00f1ee7b <
    6fedb2eaff77554ca7a0deffd2e8bc0d6e8b38b0
  - >-
    Linux >= 7919d0a27f1e7cb324e023776aa1cbff00f1ee7b <
    9026932ac8be4d0ae01db47f23619a98cc57b671
  - Linux 4.9
published: '2026-09-16'
updated: '2026-09-21'
sourceUpdated: '2026-09-21T14:17:27.843'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-90036'
references:
  - url: 'https://git.kernel.org/stable/c/6fedb2eaff77554ca7a0deffd2e8bc0d6e8b38b0'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7081224a59a0ca4edcd62c068588f4d900199a18'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/9026932ac8be4d0ae01db47f23619a98cc57b671'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/cd489b03587378645fe0d20142a33f1ed60bac98'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
epss: 0.00652
epssPercentile: 0.49031
ingestedAt: '2026-09-16T10:53:53.934Z'
---

## Overview

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

NFSD: Prevent client use-after-free during blocked-lock reaping

A bare lock owner -- its only remaining reference a blocked lock on
nn->blocked_locks_lru -- holds a raw pointer to its nfs4_client but
no reference keeping the client alive. When the per-net laundromat
reaps such a lock, freeing the nbl drops the owner reference
held through flc_owner, and the final nfs4_put_stateowner()
takes the client's cl_lock. Because the laundromat detaches the
nbl first, __destroy_client() no longer finds it, so a concurrent
force_expire_client() can free the client before nfs4_put_stateowner()
runs, dereferencing cl_lock in freed memory.

Pin the client with cl_rpc_users before dropping
nn->blocked_locks_lock, and skip clients already expiring, whose
blocked locks __destroy_client() frees while holding an owner
reference. Take nn->client_lock outside nn->blocked_locks_lock.
Every other site holds nn->blocked_locks_lock as a leaf, acquiring
no further lock, so placing nn->client_lock outside it cannot form
a lock-order cycle.

## Remediation

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