---
id: CVE-2026-74521
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ksmbd: use memcmp() to compare ClientGUIDs

  ClientGUID is a fixed-size binary value and can contain embedded NUL
  bytes
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ksmbd: use memcmp() to compare ClientGUIDs

  ClientGUID is a fixed-size binary value and can contain embedded NUL
  bytes. strncmp() stops comparing at the first NUL byte,…
severity: critical
cvss: 9.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <
    ba2a5b66f1d414eb8403d655f8813783892cfc85
  - >-
    Linux >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <
    a386c83043015a703e227775f778e40343f45911
  - >-
    Linux >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <
    d535363299822c5caa543787b21bd5cfa3e41949
  - >-
    Linux >= e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 <
    e8bb506e6ef749ac0336f3e579d8d02396b7d832
  - Linux 5.15
published: '2026-08-15'
updated: '2026-09-21'
sourceUpdated: '2026-09-21T14:17:19.380'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-74521'
references:
  - url: 'https://git.kernel.org/stable/c/a386c83043015a703e227775f778e40343f45911'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/ba2a5b66f1d414eb8403d655f8813783892cfc85'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/d535363299822c5caa543787b21bd5cfa3e41949'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e8bb506e6ef749ac0336f3e579d8d02396b7d832'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
epss: 0.00522
epssPercentile: 0.41884
ingestedAt: '2026-09-21T13:37:22.837Z'
---

## Overview

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

ksmbd: use memcmp() to compare ClientGUIDs

ClientGUID is a fixed-size binary value and can contain embedded NUL
bytes. strncmp() stops comparing at the first NUL byte, so different
ClientGUID values can incorrectly be treated as equal.

Use memcmp() in SMB3 multichannel session binding and
FSCTL_VALIDATE_NEGOTIATE_INFO to compare all SMB2_CLIENT_GUID_SIZE
bytes.

## Remediation

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