Improper access control in Linux kernel - CVE-2026-64394

CSH
CYBERSECURITY HELP
Sign In REGISTER
 
Main Vulnerability Database Vulnerabilities #VU139581

Improper access control in Linux kernel - CVE-2026-64394

Published: July 27, 2026


Vulnerability identifier: #VU139581
CSH Severity: Medium
CVSS v4: 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]
CVE-ID: CVE-2026-64394
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote user to modify file access control metadata to grant additional access.

The vulnerability exists due to improper access control in smb2_set_info_sec() when handling SMB2_SET_INFO requests with InfoType SMB2_O_INFO_SECURITY. A remote user can send a specially crafted SMB2_SET_INFO request over a handle opened with FILE_WRITE_ATTRIBUTES only to modify file access control metadata to grant additional access.

The issue affects the SECURITY arm of SMB2 SET_INFO, where no per-handle check for FILE_WRITE_DAC or FILE_WRITE_OWNER is performed before rewriting the file's owner or DACL.


Affected software

Linux kernel
Ubuntu
linux (Ubuntu package)
linux-azure (Ubuntu package)
linux-gcp-7.0 (Ubuntu package)
linux-oracle-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)
linux-azure-7.0 (Ubuntu package)

How to mitigate CVE-2026-64394

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
linux (Ubuntu package) - addressed in versions 7.0.0-31.31, 7.0.0-31.31.1, 7.0.0-31.31~24.04.1, 7.0.0-1006.7, 7.0.0-1011.11~24.04.1, 7.0.0-1012.12, 7.0.0-1012.12~24.04.1
linux-azure (Ubuntu package) - addressed in versions 7.0.0-1011.11, 7.0.0-1014.14
linux-gcp-7.0 (Ubuntu package) - update to 7.0.0-1011.11~24.04.1
linux-oracle-7.0 (Ubuntu package) - update to 7.0.0-1011.11~24.04.1
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1013.13
linux-azure-7.0 (Ubuntu package) - update to 7.0.0-1014.14~24.04.1

External References

Related Security Bulletins