Improper access control in Linux kernel - CVE-2026-64388

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

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.

Linux kernel
SUSE Linux Enterprise Workstation Extension 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise High Availability Extension 15
SUSE Linux Enterprise Desktop 15
Legacy Module
SUSE Linux Enterprise Live Patching
Public Cloud Module
Development Tools Module
Basesystem Module
openEuler
Ubuntu
kernel-livepatch-SLE15-SP7_Update_21-debugsource
kernel-livepatch-6_4_0-150700_53_81-default-debuginfo
kernel-livepatch-6_4_0-150700_53_81-default
bpftool
kernel
python3-perf-debuginfo
python3-perf
python2-perf-debuginfo
python2-perf
perf-debuginfo
perf
kernel-tools-devel
kernel-tools-debuginfo
kernel-tools
kernel-source
kernel-devel
kernel-debugsource
kernel-debuginfo
bpftool-debuginfo
kernel-headers
kernel-obs-build-debugsource
kernel-zfcpdump-debugsource
kernel-obs-build
kernel-syms
kernel-docs
kernel-64kb-debugsource
kernel-64kb-devel-debuginfo
kernel-64kb-devel
kernel-64kb-debuginfo
kernel-64kb
kernel-zfcpdump-debuginfo
reiserfs-kmp-default
reiserfs-kmp-default-debuginfo
kernel-default-livepatch
kernel-default-livepatch-devel
kernel-azure
kernel-azure-devel
kernel-azure-debugsource
kernel-azure-debuginfo
kernel-azure-devel-debuginfo
kernel-default-extra-debuginfo
kernel-default-extra
gfs2-kmp-default
cluster-md-kmp-default
kernel-default-debuginfo
ocfs2-kmp-default-debuginfo
dlm-kmp-default-debuginfo
ocfs2-kmp-default
gfs2-kmp-default-debuginfo
dlm-kmp-default
kernel-default-debugsource
kernel-default
kernel-default-devel-debuginfo
kernel-default-devel
kernel-macros
kernel-zfcpdump
cluster-md-kmp-default-debuginfo
kernel-default-base
linux (Ubuntu package)
linux-gcp-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
kernel-livepatch-SLE15-SP7_Update_21-debugsource - update to 1-150700.15.3.1
kernel-livepatch-6_4_0-150700_53_81-default-debuginfo - update to 1-150700.15.3.1
kernel-livepatch-6_4_0-150700_53_81-default - update to 1-150700.15.3.1
bpftool - addressed in versions 4.19.90-2608.3.0.0385, 5.10.0-329.0.0.230
kernel - addressed in versions 4.19.90-2608.3.0.0385, 5.10.0-329.0.0.230
python3-perf-debuginfo - addressed in versions 4.19.90-2608.3.0.0385, 5.10.0-329.0.0.230
python3-perf - addressed in versions 4.19.90-2608.3.0.0385, 5.10.0-329.0.0.230
python2-perf-debuginfo - update to 4.19.90-2608.3.0.0385
python2-perf - update to 4.19.90-2608.3.0.0385
perf-debuginfo - addressed in versions 4.19.90-2608.3.0.0385, 5.10.0-329.0.0.230
perf - addressed in versions 4.19.90-2608.3.0.0385, 5.10.0-329.0.0.230
kernel-tools-devel - addressed in versions 4.19.90-2608.3.0.0385, 5.10.0-329.0.0.230
kernel-tools-debuginfo - addressed in versions 4.19.90-2608.3.0.0385, 5.10.0-329.0.0.230
kernel-tools - addressed in versions 4.19.90-2608.3.0.0385, 5.10.0-329.0.0.230
kernel-source - addressed in versions 4.19.90-2608.3.0.0385, 5.10.0-329.0.0.230
kernel-devel - addressed in versions 4.19.90-2608.3.0.0385, 5.10.0-329.0.0.230
kernel-debugsource - addressed in versions 4.19.90-2608.3.0.0385, 5.10.0-329.0.0.230
kernel-debuginfo - addressed in versions 4.19.90-2608.3.0.0385, 5.10.0-329.0.0.230
bpftool-debuginfo - addressed in versions 4.19.90-2608.3.0.0385, 5.10.0-329.0.0.230
kernel-headers - update to 5.10.0-329.0.0.230
kernel-obs-build-debugsource - update to 6.4.0-150700.53.81.1
kernel-zfcpdump-debugsource - update to 6.4.0-150700.53.81.1
kernel-obs-build - update to 6.4.0-150700.53.81.1
kernel-syms - update to 6.4.0-150700.53.81.1
kernel-docs - update to 6.4.0-150700.53.81.1
kernel-64kb-debugsource - update to 6.4.0-150700.53.81.1
kernel-64kb-devel-debuginfo - update to 6.4.0-150700.53.81.1
kernel-64kb-devel - update to 6.4.0-150700.53.81.1
kernel-64kb-debuginfo - update to 6.4.0-150700.53.81.1
kernel-64kb - update to 6.4.0-150700.53.81.1
kernel-zfcpdump-debuginfo - update to 6.4.0-150700.53.81.1
kernel-source - update to 6.4.0-150700.53.81.1
reiserfs-kmp-default - update to 6.4.0-150700.53.81.1
reiserfs-kmp-default-debuginfo - update to 6.4.0-150700.53.81.1
kernel-default-livepatch - update to 6.4.0-150700.53.81.1
kernel-default-livepatch-devel - update to 6.4.0-150700.53.81.1
kernel-azure - update to 6.4.0-150700.53.81.1
kernel-azure-devel - update to 6.4.0-150700.53.81.1
kernel-azure-debugsource - update to 6.4.0-150700.53.81.1
kernel-azure-debuginfo - update to 6.4.0-150700.53.81.1
kernel-azure-devel-debuginfo - update to 6.4.0-150700.53.81.1
kernel-default-extra-debuginfo - update to 6.4.0-150700.53.81.1
kernel-default-extra - update to 6.4.0-150700.53.81.1
kernel-devel - update to 6.4.0-150700.53.81.1
gfs2-kmp-default - update to 6.4.0-150700.53.81.1
cluster-md-kmp-default - update to 6.4.0-150700.53.81.1
kernel-default-debuginfo - update to 6.4.0-150700.53.81.1
ocfs2-kmp-default-debuginfo - update to 6.4.0-150700.53.81.1
dlm-kmp-default-debuginfo - update to 6.4.0-150700.53.81.1
ocfs2-kmp-default - update to 6.4.0-150700.53.81.1
gfs2-kmp-default-debuginfo - update to 6.4.0-150700.53.81.1
dlm-kmp-default - update to 6.4.0-150700.53.81.1
kernel-default-debugsource - update to 6.4.0-150700.53.81.1
kernel-default - update to 6.4.0-150700.53.81.1
kernel-default-devel-debuginfo - update to 6.4.0-150700.53.81.1
kernel-default-devel - update to 6.4.0-150700.53.81.1
kernel-macros - update to 6.4.0-150700.53.81.1
kernel-zfcpdump - update to 6.4.0-150700.53.81.1
cluster-md-kmp-default-debuginfo - update to 6.4.0-150700.53.81.1
kernel-default-base - update to 6.4.0-150700.53.81.1.150700.17.45.1
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-gcp-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

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

• Improper access control in Linux kernel smb client
• openEuler 20.03 LTS SP4 update for kernel
• openEuler 22.03 LTS SP4 update for kernel
• Ubuntu update for linux-oem-7.0
• Ubuntu update for linux
• Ubuntu update for linux-gcp-7.0
• SUSE update for the Linux Kernel