In the Linux kernel, the following vulnerability has been resolved: smb/client: fix chown/chgrp with SMB3 POSIX Extensions Ownership (chown) and group (chgrp) modifications were being ignored when mounting with SMB3 POSIX Extensions unless CIFS_MOUNT_CIFS_ACL or CIFS_MOUNT_MODE_FROM_SID were also explicitly set. Fix this by checking for posix_extensions in cifs_setattr_nounix() when updating UID and GID, ensuring that id_mode_to_cifs_acl() is called to map and set the ownership/group information on the server.

A flaw was found in the Linux kernel's Server Message Block (SMB) client. When mounting filesystems using SMB3 POSIX Extensions, modifications to file ownership (chown) and group (chgrp) were not correctly applied on the server unless specific mount options were also enabled. This could allow a local user to set incorrect file permissions, potentially leading to unauthorized access to sensitive information or unintended privilege escalation.

Red Hat Enterprise Linux 10 Fix deferred kernel Red Hat Enterprise Linux 6 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel-rt Red Hat Enterprise Linux 8 Fix deferred kernel Red Hat Enterprise Linux 8 Fix deferred kernel-rt Red Hat Enterprise Linux 9 Fix deferred kernel Red Hat Enterprise Linux 9 Fix deferred kernel-rt https://www.cve.org/CVERecord?id=CVE-2026-64388 https://nvd.nist.gov/vuln/detail/CVE-2026-64388 https://lore.kernel.org/linux-cve-announce/2026072527-CVE-2026-64388-82d9@gregkh/T