Improper access control in Linux kernel - CVE-2026-64388
Published: July 27, 2026
Vulnerability identifier: #VU139575
CSH Severity: Low
CVSS v4: 4.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-64388
CWE-ID: CWE-284
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a local user to bypass ownership and group changes.
The vulnerability exists due to improper access control in cifs_setattr_nounix() when processing chown and chgrp operations on mounts using SMB3 POSIX Extensions. A local user can change file ownership or group attributes in a way that is ignored to bypass ownership and group changes.
The issue occurs only when SMB3 POSIX Extensions are used without the relevant ACL or SID-based mount options enabled.
Affected software
Linux kernel
How to mitigate CVE-2026-64388
Install security update from vendor's repository.
Linux kernel - update to 7.0 rc3