SB20260727178 - Improper access control in Linux kernel smb client

Description

This security bulletin contains information about 1 vulnerability.

1) Improper access control (CVE-ID: CVE-2026-64388)

CWE-ID: CWE-284 - Improper Access Control

CVSSv4: 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]

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.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/550cfb8a81181331d4d0f76ab75ee58a0bf41e3e
• https://git.kernel.org/stable/c/760ef2c579c2609cf17fb1cd5392f64d42d43d33