SB20260720330 - Out-of-bounds read in Linux kernel smb server

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Main Vulnerability Database SB20260720330

SB20260720330 - Out-of-bounds read in Linux kernel smb server

Published: July 20, 2026

Security Bulletin ID SB20260720330
CSH Severity
Medium
Patch available
YES
Number of vulnerabilities 1
Exploitation vector Remote access
Highest impact Information disclosure

Breakdown by Severity

Medium 100%
  • Low
  • Medium
  • High
  • Critical

Description

This security bulletin contains information about 1 vulnerability.


1) Out-of-bounds read (CVE-ID: CVE-2026-63909)

CWE-ID: CWE-125 - Out-of-bounds read

CVSSv4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N]


The vulnerability allows a remote attacker to disclose sensitive information.

The vulnerability exists due to an out-of-bounds read in smb_check_perm_dacl() ACE-walk loops in ksmbd when processing SMB2_CREATE operations with a crafted security descriptor. A remote attacker can send a specially crafted request to disclose sensitive information.

The issue is caused by a transposed bounds check that can leave the loop guard ineffective and permit reading ace->size even when only 0 to 3 bytes remain in the ACE data.


Remediation

Install update from vendor's website.

References