---
id: CVE-2026-89713
title: 'NFSD: check truncate permission under inode lock'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  NFSD: check truncate permission under inode lock

  nfsd_setattr() checks whether a size update needs NFSD_MAY_TRUNC
  before it takes inode_lock(). The comparison uses the…
severity: critical
cvss: 9.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H'
cvssSource: cna
cwe:
  - CWE-367
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 783112f7401ff449d979530209b3f6c2594fdb4e <
    52d0c5bdfe232c9974d4b11f97078b9c7814f05d
  - >-
    Linux >= 783112f7401ff449d979530209b3f6c2594fdb4e <
    3afa17d93ba8c925f49370c816c6dae5112d8c24
  - >-
    Linux >= 783112f7401ff449d979530209b3f6c2594fdb4e <
    d8352da196349182e1afd5a93308256cddc0a97d
  - >-
    Linux >= 783112f7401ff449d979530209b3f6c2594fdb4e <
    44086254479035de42ca3d286ecf25521d4e6325
  - >-
    Linux >= 783112f7401ff449d979530209b3f6c2594fdb4e <
    b778e0e0a16759f22a70579c3cf8d254a40d4a7f
  - Linux 604a3c407026d6162d15300478e63f901e435efc
  - Linux cc4d5dc73841b98d33cdfb9822d70b0aac4beca5
  - Linux 3ee4f442e5b37a537297b812557b1163f96b5399
  - Linux a3c6cbc4eac4473ed5461d5faae2794d3e5c0e44
  - Linux 982898d7f97a35447403c3fcecc0d96c646ce101
  - Linux >= 3.2.89 < 3.3
  - Linux >= 3.16.44 < 3.17
  - Linux >= 4.4.53 < 4.5
  - Linux >= 4.9.14 < 4.10
  - Linux >= 4.10.2 < 4.11
  - Linux 4.11
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-16T19:26:29.958634Z'
published: '2026-09-11'
updated: '2026-10-21'
sourceUpdated: '2026-10-21T12:48:27.026Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-89713'
references:
  - url: 'https://git.kernel.org/stable/c/52d0c5bdfe232c9974d4b11f97078b9c7814f05d'
  - url: 'https://git.kernel.org/stable/c/3afa17d93ba8c925f49370c816c6dae5112d8c24'
  - url: 'https://git.kernel.org/stable/c/d8352da196349182e1afd5a93308256cddc0a97d'
  - url: 'https://git.kernel.org/stable/c/44086254479035de42ca3d286ecf25521d4e6325'
  - url: 'https://git.kernel.org/stable/c/b778e0e0a16759f22a70579c3cf8d254a40d4a7f'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89713.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89713'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532459'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89713'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89713'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89713.mbox
tags:
  - cve.org
  - csaf
  - vex
  - red-hat
  - score-dispute
epss: 0.00612
epssPercentile: 0.49082
scores:
  cna: 9.1
  vendor: 7
ingestedAt: '2026-09-14T15:23:07.472Z'
---

## Overview

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

NFSD: check truncate permission under inode lock

nfsd_setattr() checks whether a size update needs NFSD_MAY_TRUNC
before it takes inode_lock(). The comparison uses the file size sampled
by that unlocked read, but the actual ATTR_SIZE update is applied later
under inode_lock() by notify_change().

This leaves a TOCTOU window for append-only files. If a client sends a
SETATTR that does not shrink the file at the time of the unlocked
sample, a concurrent append can extend the file before nfsd_setattr()
takes inode_lock(). notify_change() then applies a real truncation
without the NFSD_MAY_TRUNC check that rejects IS_APPEND(inode). The VFS
truncate syscall paths perform their own append-only checks before
calling notify_change(), so NFSD must make this decision against the
locked size it is about to change.

Split the write-count acquisition from the truncation permission check.
Keep get_write_access() before the locked setattr work, then recheck
whether the requested size is below i_size_read(inode) after inode_lock()
has been acquired and before notify_change(ATTR_SIZE). This also avoids
the plain unlocked inode->i_size load.

## Affected

- `Linux >= 783112f7401ff449d979530209b3f6c2594fdb4e < 52d0c5bdfe232c9974d4b11f97078b9c7814f05d`
- `Linux >= 783112f7401ff449d979530209b3f6c2594fdb4e < 3afa17d93ba8c925f49370c816c6dae5112d8c24`
- `Linux >= 783112f7401ff449d979530209b3f6c2594fdb4e < d8352da196349182e1afd5a93308256cddc0a97d`
- `Linux >= 783112f7401ff449d979530209b3f6c2594fdb4e < 44086254479035de42ca3d286ecf25521d4e6325`
- `Linux >= 783112f7401ff449d979530209b3f6c2594fdb4e < b778e0e0a16759f22a70579c3cf8d254a40d4a7f`
- `Linux 604a3c407026d6162d15300478e63f901e435efc`
- `Linux cc4d5dc73841b98d33cdfb9822d70b0aac4beca5`
- `Linux 3ee4f442e5b37a537297b812557b1163f96b5399`
- `Linux a3c6cbc4eac4473ed5461d5faae2794d3e5c0e44`
- `Linux 982898d7f97a35447403c3fcecc0d96c646ce101`
- `Linux >= 3.2.89 < 3.3`
- `Linux >= 3.16.44 < 3.17`
- `Linux >= 4.4.53 < 4.5`
- `Linux >= 4.9.14 < 4.10`
- `Linux >= 4.10.2 < 4.11`
- `Linux 4.11`

## 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 9, Red Hat OpenShift Container Platform 4, Red Hat Enterprise Linux 7, … · updated 2026-09-21 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89713.json)