---
id: CVE-2026-53392
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  NFSv4/flexfiles: reject zero filehandle version count

  ff_layout_alloc_lseg() decodes the filehandle-version array count
  from the flexfiles layout body
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  NFSv4/flexfiles: reject zero filehandle version count

  ff_layout_alloc_lseg() decodes the filehandle-version array count
  from the flexfiles layout body. The value is us…
severity: none
published: '2026-07-19'
updated: '2026-07-19'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-53392'
references:
  - url: 'https://git.kernel.org/stable/c/2131ed64b767ffa8bcdb3677d90f3964e39aabc8'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/2c6bb3c40bc24f6aa8dfbe6fe98c3ad6389203f2'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7779c85028a0676fb190cde4f0c540f4f8e97761'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/d8c90c7cc061265d5f2813a1f5c82ef2f4707e67'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
ingestedAt: '2026-07-19T21:33:34.561Z'
epss: 0.00529
epssPercentile: 0.43726
---

## Overview

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

NFSv4/flexfiles: reject zero filehandle version count

ff_layout_alloc_lseg() decodes the filehandle-version array count
from the flexfiles layout body. The value is used as the count for
kzalloc_objs(), and the current code only rejects NULL.

A zero count yields ZERO_SIZE_PTR, which can be stored in
dss_info->fh_versions even though later flexfiles paths assume that at
least one filehandle version exists.

Reject fh_count == 0 before the allocation, matching the existing zero
version_count validation in the flexfiles GETDEVICEINFO parser.

A QEMU/KASAN run with a malformed flexfiles layout hit:

  KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
  RIP: 0010:ff_layout_encode_ff_layoutupdate.isra.0+0x15f/0x750
  ff_layout_encode_layoutreturn+0x683/0x970
  nfs4_xdr_enc_layoutreturn+0x278/0x3a0
  Kernel panic - not syncing: Fatal exception

The patched kernel rejects the malformed layout without KASAN/oops/panic,
and a valid fh_count=1 regression still opens, reads, and unmounts cleanly.

## Remediation

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