SB20260727167 - Improper access control in Linux kernel smb server

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Main Vulnerability Database SB20260727167

SB20260727167 - Improper access control in Linux kernel smb server

Published: July 27, 2026

Security Bulletin ID SB20260727167
CSH Severity
Medium
Patch available
YES
Number of vulnerabilities 1
Exploitation vector Remote access
Highest impact Data manipulation

Breakdown by Severity

Medium 100%
  • Low
  • Medium
  • High
  • Critical

Description

This security bulletin contains information about 1 vulnerability.


1) Improper access control (CVE-ID: CVE-2026-64398)

CWE-ID: CWE-284 - Improper Access Control

CVSSv4: 7.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N]


The vulnerability allows a remote user to modify file data without the required file write permission.

The vulnerability exists due to improper access control in smb2_ioctl() when processing FSCTL_SET_ZERO_DATA requests. A remote user can use a handle opened with only FILE_WRITE_ATTRIBUTES to zero file data and modify file contents without the required FILE_WRITE_DATA right.

The issue affects ksmbd, and the advisory states it was reproduced by an authenticated SMB client using a handle that was granted FILE_WRITE_ATTRIBUTES but not FILE_WRITE_DATA.


Remediation

Install update from vendor's website.

References