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High · 7.8 CVE-2026-89638 EUVD-2026-76550GHSA-7hx7-9jhj-445w

smb: client: clear setuid/setgid bit on write with cifsacl/modefromsid/posix extensions

Published Sep 11, 2026 · Updated Oct 30, 2026 · Assigned by Linux

Vendor: Linux Product: Linux Package: kernel Package: linux Package: linux Package: linux-6.12 Package: linux-allwinner-5.19 Package: linux-aws Package: linux-aws-5.0 Package: linux-aws-5.11 Package: linux-aws-5.13 Package: linux-aws-5.15 Package: linux-aws-5.19 Package: linux-aws-5.3 Package: linux-aws-5.4 Package: linux-aws-5.8 Package: linux-aws-6.14 Package: linux-aws-6.17 Package: linux-aws-6.2 Package: linux-aws-6.5 Package: linux-aws-6.8 Package: linux-aws-7.0 Package: linux-aws-fips Package: linux-aws-hwe Package: linux-azure Package: linux-azure-4.15 Package: linux-azure-5.11 Package: linux-azure-5.13 Package: linux-azure-5.15 Package: linux-azure-5.19 Package: linux-azure-5.3 Package: linux-azure-5.4 Package: linux-azure-5.8 Package: linux-azure-6.11 Package: linux-azure-6.14 Package: linux-azure-6.17 Package: linux-azure-6.2 Package: linux-azure-6.5 Package: linux-azure-6.8 Package: linux-azure-7.0 Package: linux-azure-edge Package: linux-azure-fde Package: linux-azure-fde-5.15 Package: linux-azure-fde-5.19 Package: linux-azure-fde-6.14 Package: linux-azure-fde-6.17 Package: linux-azure-fde-6.2 Package: linux-azure-fde-6.8 Package: linux-azure-fde-7.0 Package: linux-azure-fips Package: linux-azure-nvidia Package: linux-azure-nvidia-6.14 Package: linux-bluefield Package: linux-fips Package: linux-gcp Package: linux-gcp-4.15 Package: linux-gcp-5.11 Package: linux-gcp-5.13 Package: linux-gcp-5.15 Package: linux-gcp-5.19 Package: linux-gcp-5.3 Package: linux-gcp-5.4 Package: linux-gcp-5.8 Package: linux-gcp-6.11 Package: linux-gcp-6.14 Package: linux-gcp-6.17 Package: linux-gcp-6.2 Package: linux-gcp-6.5 Package: linux-gcp-6.8 Package: linux-gcp-7.0 Package: linux-gcp-fips Package: linux-gke Package: linux-gke-4.15 Package: linux-gke-5.15 Package: linux-gke-5.4 Package: linux-gkeop Package: linux-gkeop-5.15 Package: linux-gkeop-5.4 Package: linux-hwe Package: linux-hwe-5.11 Package: linux-hwe-5.13 Package: linux-hwe-5.15 Package: linux-hwe-5.19 Package: linux-hwe-5.4 Package: linux-hwe-5.8 Package: linux-hwe-6.11 Package: linux-hwe-6.14 Package: linux-hwe-6.17 Package: linux-hwe-6.2 Package: linux-hwe-6.5 Package: linux-hwe-6.8 Package: linux-hwe-7.0 Package: linux-hwe-edge Package: linux-ibm Package: linux-ibm-5.15 Package: linux-ibm-5.4 Package: linux-ibm-6.8 Package: linux-intel-5.13 Package: linux-intel-iot-realtime Package: linux-intel-iotg Package: linux-intel-iotg-5.15 Package: linux-iot Package: linux-kvm Package: linux-lowlatency Package: linux-lowlatency-hwe-5.15 Package: linux-lowlatency-hwe-5.19 Package: linux-lowlatency-hwe-6.11 Package: linux-lowlatency-hwe-6.2 Package: linux-lowlatency-hwe-6.5 Package: linux-lowlatency-hwe-6.8 Package: linux-lts-xenial Package: linux-nvidia Package: linux-nvidia-6.11 Package: linux-nvidia-6.17 Package: linux-nvidia-6.2 Package: linux-nvidia-6.5 Package: linux-nvidia-6.8 Package: linux-nvidia-7.0 Package: linux-nvidia-bos Package: linux-nvidia-lowlatency Package: linux-nvidia-tegra Package: linux-nvidia-tegra-5.15 Package: linux-nvidia-tegra-igx Package: linux-oem Package: linux-oem-5.10 Package: linux-oem-5.13 Package: linux-oem-5.14 Package: linux-oem-5.17 Package: linux-oem-5.6 Package: linux-oem-6.0 Package: linux-oem-6.1 Package: linux-oem-6.11 Package: linux-oem-6.14 Package: linux-oem-6.17 Package: linux-oem-6.5 Package: linux-oem-6.8 Package: linux-oem-7.0 Package: linux-oracle Package: linux-oracle-5.0 Package: linux-oracle-5.11 Package: linux-oracle-5.13 Package: linux-oracle-5.15 Package: linux-oracle-5.3 Package: linux-oracle-5.4 Package: linux-oracle-5.8 Package: linux-oracle-6.14 Package: linux-oracle-6.17 Package: linux-oracle-6.5 Package: linux-oracle-6.8 Package: linux-oracle-7.0 Package: linux-raspi Package: linux-raspi-5.4 Package: linux-raspi-realtime Package: linux-raspi2 Package: linux-realtime Package: linux-realtime-6.14 Package: linux-realtime-6.17 Package: linux-realtime-6.8 Package: linux-riscv Package: linux-riscv-5.11 Package: linux-riscv-5.15 Package: linux-riscv-5.19 Package: linux-riscv-5.8 Package: linux-riscv-6.14 Package: linux-riscv-6.17 Package: linux-riscv-6.5 Package: linux-riscv-6.8 Package: linux-riscv-7.0 Package: linux-starfive-5.19 Package: linux-starfive-6.2 Package: linux-starfive-6.5 Package: linux-vmware Package: linux-xilinx Package: linux-xilinx-zynqmp Platform: Linux Ecosystem: Azure Linux Ecosystem: Debian Ecosystem: Ubuntu

Description

In the Linux kernel, the following vulnerability has been resolved:

smb: client: clear setuid/setgid bit on write with cifsacl/modefromsid/posix extensions

When a file has the setuid or setgid bit set and is written to, the VFS
strips those bits and issues a setattr with ATTR_KILL_SUID/ATTR_KILL_SGID
together with an ATTR_MODE carrying the already-cleared mode.

Both cifs_setattr_unix() and cifs_setattr_nounix() unconditionally dropped
ATTR_MODE in that case:

/* skip mode change if it's just for clearing setuid/setgid */
if (attrs->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
attrs->ia_valid &= ~ATTR_MODE;

This is fine for the default mount, where the mode is only emulated via
the DOS read-only attribute and cannot represent the setuid/setgid bits
anyway. However, with the "cifsacl" or "modefromsid" mount options the
mode is stored on the server through an ACL (id_mode_to_cifs_acl()), with
the SMB3.1.1 POSIX extensions the mode is sent to the server directly,
and with the SMB1 Unix extensions (cifs_setattr_unix) the mode is sent
via CIFSSMBUnixSetPathInfo(). In all those cases dropping ATTR_MODE means
the cleared mode is never pushed to the server, so the setuid/setgid bit
survives the write.

This is a security issue: on local filesystems the setuid bit is stripped
when a file is written, but over these cifs.ko mounts the bit persists on
the server, potentially allowing an unexpected privilege escalation on
subsequent execution.

Fix this in two places:

1. cifs_setattr_nounix(): only take the "skip mode change" shortcut
when the mode is emulated via the DOS read-only attribute (i.e.
neither cifsacl/modefromsid nor the SMB3.1.1 POSIX extensions are
in effect), so that the cleared mode is propagated to the server
in the ACL / POSIX cases.

2. cifs_setattr_unix(): this function is only called when Unix
extensions are in effect, so the mode is always stored on the
server. Remove the shortcut entirely so that the cleared mode is
always pushed.

Affected products

VendorProductAffectedFixed
Linux Linux 2.6.24 5.10.273

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

ReleasePackageFixed inAdvisory
Debian 14 linux 7.2.6-1 —
Debian 13 linux 6.12.113-1 —
Debian 12 linux No fix yet —
Debian 12 linux-6.12 6.12.113-1~deb12u1 —
ReleasePackageFixed inAdvisory
Ubuntu Nvidia-BlueField 24.04 LTS linux-bluefield 6.8.0-1036.41 —
Ubuntu Nvidia-BlueField 22.04 LTS linux-bluefield No fix yet —
Ubuntu 26.04 LTS linux 7.0.0-42.42 USN-8959-1
Ubuntu 26.04 LTS linux-aws 7.0.0-1016.17 USN-8959-1
Ubuntu 26.04 LTS linux-azure 7.0.0-1020.21 USN-9019-1
Ubuntu 26.04 LTS linux-azure-fde 7.0.0-1019.19 USN-9020-1
Ubuntu 26.04 LTS linux-gcp 7.0.0-1016.18 USN-8959-1
Ubuntu 26.04 LTS linux-gke 7.0.0-1010.11 USN-9020-1
Ubuntu 26.04 LTS linux-ibm +1 7.0.0-1017.17 USN-8960-1, USN-8959-1
Ubuntu 26.04 LTS linux-nvidia +1 No fix yet —
Ubuntu 26.04 LTS linux-oracle 7.0.0-1015.16 USN-8959-1
Ubuntu 26.04 LTS linux-raspi 7.0.0-1023.23 USN-9021-1
Ubuntu 26.04 LTS linux-realtime 7.0.0-43.43.1 USN-9020-1
Ubuntu 26.04 LTS linux-riscv 7.0.0-42.42.1 —
Ubuntu 24.04 LTS linux 6.8.0-149.149 USN-9022-1
Ubuntu 24.04 LTS linux-aws 6.8.0-1069.74 USN-9022-1
Ubuntu 24.04 LTS linux-aws-7.0 7.0.0-1017.18~24.04.1 USN-9020-1
Ubuntu 24.04 LTS linux-azure 6.8.0-1073.82 USN-9022-1
Ubuntu 24.04 LTS linux-azure-fde 6.8.0-1071.78 USN-9039-1
Ubuntu 24.04 LTS linux-azure-fde-7.0 7.0.0-1019.19~24.04.1 USN-9020-1
Ubuntu 24.04 LTS linux-gcp 6.8.0-1073.81 USN-9022-1
Ubuntu 24.04 LTS linux-gcp-7.0 7.0.0-1017.19~24.04.1 USN-9020-1
Ubuntu 24.04 LTS linux-gke 6.8.0-1068.77 USN-9022-1
Ubuntu 24.04 LTS linux-gkeop 6.8.0-1053.57 USN-9023-1
Ubuntu 24.04 LTS linux-hwe-7.0 7.0.0-42.42~24.04.1 USN-8959-1
Ubuntu 24.04 LTS linux-ibm 6.8.0-1069.70 USN-9022-1
Ubuntu 24.04 LTS linux-lowlatency 6.8.0-149.149.1 USN-9022-1
Ubuntu 24.04 LTS linux-nvidia 6.8.0-1067.70 USN-9024-1
Ubuntu 24.04 LTS linux-nvidia-lowlatency 6.8.0-1067.70.1 USN-9040-1
Ubuntu 24.04 LTS linux-nvidia-tegra 6.8.0-1038.42 USN-9002-1
Ubuntu 24.04 LTS linux-oracle 6.8.0-1067.71 USN-9022-1
Ubuntu 24.04 LTS linux-oracle-7.0 7.0.0-1016.18~24.04.1 USN-9020-1
Ubuntu 24.04 LTS linux-raspi 6.8.0-1068.72 USN-9025-1
Ubuntu 24.04 LTS linux-riscv +31 No fix yet —
Ubuntu 24.04 LTS linux-riscv-7.0 7.0.0-42.42.1~24.04.1 —
Ubuntu 24.04 LTS linux-vmware 6.8.0-1010.10 USN-9022-1
Ubuntu 22.04 LTS linux +50 No fix yet —
Ubuntu 22.04 LTS linux-aws-6.8 6.8.0-1069.74~22.04.1 USN-9024-1
Ubuntu 22.04 LTS linux-azure-6.8 6.8.0-1073.82~22.04.1 USN-9026-1
Ubuntu 22.04 LTS linux-azure-fde-6.8 6.8.0-1071.78~22.04.1 USN-9026-1
Ubuntu 22.04 LTS linux-gcp-6.8 6.8.0-1073.81~22.04.1 USN-9024-1
Ubuntu 22.04 LTS linux-hwe-6.8 6.8.0-149.149~22.04.1 USN-9066-1
Ubuntu 22.04 LTS linux-ibm-6.8 6.8.0-1069.70~22.04.1 USN-9024-1
Ubuntu 22.04 LTS linux-lowlatency-hwe-6.8 6.8.0-149.149.1~22.04.1 USN-9024-1
Ubuntu 22.04 LTS linux-oracle-6.8 6.8.0-1067.71~22.04.1 USN-9025-1
Ubuntu 22.04 LTS linux-riscv-6.8 6.8.0-149.149~22.04.2 —
Show 18 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
Ubuntu 20.04 LTS linux-gke +28 No fix yet —
Ubuntu 18.04 LTS linux-gcp +14 No fix yet —
Ubuntu 16.04 LTS linux-hwe-edge No fix yet —
Ubuntu Pro Realtime 24.04 LTS linux-raspi-realtime 6.8.0-2056.58 USN-9025-1
Ubuntu Pro Realtime 24.04 LTS linux-realtime 6.8.1-1064.65 USN-9023-1
Ubuntu Pro Realtime 24.04 LTS linux-realtime-6.14 +1 No fix yet —
Ubuntu Pro Realtime 22.04 LTS linux-realtime +1 No fix yet —
Ubuntu Pro Realtime 22.04 LTS linux-realtime-6.8 6.8.1-1064.65~22.04.1 USN-9024-1
Ubuntu Pro FIPS 20.04 LTS linux-fips +3 No fix yet —
Ubuntu Pro FIPS 18.04 LTS linux-fips +3 No fix yet —
Ubuntu Pro FIPS 16.04 LTS linux-fips No fix yet —
Ubuntu Pro FIPS-updates 24.04 LTS linux-aws-fips 6.8.0-1069.74+fips1 USN-9023-1
Ubuntu Pro FIPS-updates 24.04 LTS linux-azure-fips 6.8.0-1073.82+fips1 USN-9022-1
Ubuntu Pro FIPS-updates 24.04 LTS linux-fips No fix yet —
Ubuntu Pro FIPS-updates 24.04 LTS linux-gcp-fips 6.8.0-1073.81+fips1 USN-9023-1
Ubuntu Pro FIPS-updates 22.04 LTS linux-fips +3 No fix yet —
Ubuntu Pro FIPS-updates 20.04 LTS linux-fips +3 No fix yet —
Ubuntu Pro FIPS-updates 18.04 LTS linux-fips +3 No fix yet —
Ubuntu Pro FIPS-updates 16.04 LTS linux-fips No fix yet —
Ubuntu Pro FIPS-preview 22.04 LTS linux-fips +3 No fix yet —
Ubuntu Pro 20.04 LTS linux +21 No fix yet —
Ubuntu Pro 18.04 LTS linux +12 No fix yet —
Ubuntu Pro 16.04 LTS linux +7 No fix yet —
Ubuntu Pro 14.04 LTS linux +3 No fix yet —

AlmaLinux

Errata ↗
ReleasePackageFixed inAdvisory
AlmaLinux 10 rv +74 6.12.0-211.69.1.el10_2 ALSA-2026:91565
AlmaLinux 9 rv +73 5.14.0-687.61.1.el9_8 ALSA-2026:90365
AlmaLinux 8 kernel-rt +9 4.18.0-553.178.1.rt7.519.el8_10 ALSA-2026:89082
AlmaLinux 8 perf +24 4.18.0-553.178.1.el8_10 ALSA-2026:89083

Rocky Linux

Errata ↗
ReleasePackageFixed inAdvisory
Rocky Linux 10 kernel 6.12.0-211.69.1.el10_2 RLSA-2026:91565
Rocky Linux 9 kernel 5.14.0-687.61.1.el9_8 RXSA-2026:90365, RLSA-2026:90365
Rocky Linux 8 kernel 4.18.0-553.178.1.el8_10 RLSA-2026:89083
Rocky Linux 8 kernel-rt 4.18.0-553.178.1.rt7.519.el8_10 RLSA-2026:89082
ReleasePackageFixed inAdvisory
SLES 15 SP7 kernel-64kb +7 6.4.0-150700.53.84.1 SUSE-SU-2026:4706-1
SLES 15 SP7 kernel-default-base 6.4.0-150700.53.84.1.150700.17.47.1 SUSE-SU-2026:4706-1
SLES 15 SP6 kernel-64kb +6 6.4.0-150600.23.138.1 SUSE-SU-2026:4660-1
SLES 15 SP6 kernel-default-base 6.4.0-150600.23.138.1.150600.12.64.1 SUSE-SU-2026:4660-1
SLES 15 SP5 kernel-64kb +4 5.14.21-150500.55.192.2 SUSE-SU-2026:4667-1
SLES 15 SP5 kernel-default-base 5.14.21-150500.55.192.2.150500.6.89.2 SUSE-SU-2026:4667-1
SLES 15 SP5 kernel-docs +1 5.14.21-150500.55.192.1 SUSE-SU-2026:4667-1
SLES 15 SP4 kernel-64kb +6 5.14.21-150400.24.243.1 SUSE-SU-2026:4668-1
SLES 15 SP4 kernel-default-base 5.14.21-150400.24.243.1.150400.24.122.1 SUSE-SU-2026:4668-1
SLES 12 SP5 kernel-syms +2 4.12.14-122.339.1 SUSE-SU-2026:5121-1
Show 17 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
SLES for SAP 15 SP6 kernel-default-base 6.4.0-150600.23.138.1.150600.12.64.1 SUSE-SU-2026:4660-1
SLES for SAP 15 SP6 kernel-docs +4 6.4.0-150600.23.138.1 SUSE-SU-2026:4660-1
SLES for SAP 15 SP5 kernel-default-base 5.14.21-150500.55.192.2.150500.6.89.2 SUSE-SU-2026:4667-1
SLES for SAP 15 SP5 kernel-docs +1 5.14.21-150500.55.192.1 SUSE-SU-2026:4667-1
SLES for SAP 15 SP5 kernel-source +2 5.14.21-150500.55.192.2 SUSE-SU-2026:4667-1
SLES for SAP 15 SP4 kernel-default-base 5.14.21-150400.24.243.1.150400.24.122.1 SUSE-SU-2026:4668-1
SLES for SAP 15 SP4 kernel-docs +4 5.14.21-150400.24.243.1 SUSE-SU-2026:4668-1
SLE Micro 6.2 podman 5.4.2-160000.6.1 SUSE-SU-2026:24182-1
SLE Micro 6.1 kernel-default-base 6.4.0-159998.53.1.159998.21.38 SUSE-SU-2026:24181-1
SLE Micro 6.1 kernel-rt +4 6.4.0-159998.53.1 SUSE-SU-2026:24182-1, SUSE-SU-2026:24181-1
SLE Micro 6.0 kernel-default-base 6.4.0-159998.53.1.159998.21.38 SUSE-SU-2026:24315-1
SLE Micro 6.0 kernel-rt +4 6.4.0-159998.53.1 SUSE-SU-2026:24316-1, SUSE-SU-2026:24315-1
SLE Micro 5.5 kernel-default-base 5.14.21-150500.55.192.2.150500.6.89.2 SUSE-SU-2026:4667-1
SLE Micro 5.5 kernel-rt +1 5.14.21-150500.13.164.1 SUSE-SU-2026:4665-1
SLE Micro 5.5 kernel-source +1 5.14.21-150500.55.192.2 SUSE-SU-2026:4667-1
SLE Micro 5.4 kernel-default-base 5.14.21-150400.24.243.1.150400.24.122.1 SUSE-SU-2026:4668-1
SLE Micro 5.4 kernel-rt +1 5.14.21-150400.15.189.1 SUSE-SU-2026:4666-1
SLE Micro 5.4 kernel-source +1 5.14.21-150400.24.243.1 SUSE-SU-2026:4668-1
SLE Micro 5.3 kernel-default-base 5.14.21-150400.24.243.1.150400.24.122.1 SUSE-SU-2026:4668-1
SLE Micro 5.3 kernel-rt +1 5.14.21-150400.15.189.1 SUSE-SU-2026:4666-1
SLE Micro 5.3 kernel-source +1 5.14.21-150400.24.243.1 SUSE-SU-2026:4668-1
SLE Live Patching 15 SP7 kernel-default 6.4.0-150700.53.84.1 SUSE-SU-2026:4706-1
SLE Live Patching 15 SP7 kernel-livepatch-SLE15-SP7-RT_Update_21 1-150700.1.3.1 SUSE-SU-2026:4640-1
SLE Live Patching 15 SP7 kernel-livepatch-SLE15-SP7_Update_22 1-150700.15.3.1 SUSE-SU-2026:4706-1
SLE Live Patching 15 SP6 kernel-default 6.4.0-150600.23.138.1 SUSE-SU-2026:4660-1
SLE Live Patching 15 SP6 kernel-livepatch-SLE15-SP6_Update_32 1-150600.13.3.1 SUSE-SU-2026:4660-1
SLE Live Patching 15 SP5 kernel-default 5.14.21-150500.55.192.2 SUSE-SU-2026:4667-1
SLE Live Patching 15 SP5 kernel-livepatch-SLE15-SP5_Update_46 1-150500.11.3.2 SUSE-SU-2026:4667-1
SLE Live Patching 15 SP4 kernel-default 5.14.21-150400.24.243.1 SUSE-SU-2026:4668-1
SLE Live Patching 15 SP4 kernel-livepatch-SLE15-SP4_Update_60 1-150400.9.3.1 SUSE-SU-2026:4668-1
SLE Live Patching 12 SP5 kernel-default 4.12.14-122.339.1 SUSE-SU-2026:5121-1
SLE Live Patching 12 SP5 kgraft-patch-SLE12-SP5_Update_90 1-8.3.1 SUSE-SU-2026:5121-1
SLE HPC 15 SP5 kernel-64kb +3 5.14.21-150500.55.192.2 SUSE-SU-2026:4667-1
SLE HPC 15 SP5 kernel-default-base 5.14.21-150500.55.192.2.150500.6.89.2 SUSE-SU-2026:4667-1
SLE HPC 15 SP5 kernel-docs +1 5.14.21-150500.55.192.1 SUSE-SU-2026:4667-1
SLE HPC 15 SP4 kernel-64kb +5 5.14.21-150400.24.243.1 SUSE-SU-2026:4668-1
SLE HPC 15 SP4 kernel-default-base 5.14.21-150400.24.243.1.150400.24.122.1 SUSE-SU-2026:4668-1
SUSE Real Time Module 15 SP7 kernel-rt +2 6.4.0-150700.7.78.1 SUSE-SU-2026:4640-1
ReleasePackageFixed inAdvisory
openSUSE Tumbleweed kernel-source 7.2.7-1.1 openSUSE-SU-2026:11880-1

Amazon Linux

ReleasePackageFixed inAdvisory
Amazon Linux 2023 kernel-livepatch-6.1.189-236.399 +2 1:1.0-0.amzn2023 ALAS2023-2026-3336, ALAS2023-2026-3335, ALAS2023-2026-3187
Amazon Linux 2023 perf +12 1:6.1.189-236.399.amzn2023 ALAS2023-2026-3336
Amazon Linux 2023 perf6.12 +11 1:6.12.113-138.209.amzn2023 ALAS2023-2026-3335
Amazon Linux 2023 perf6.18 +12 1:6.18.51-120.162.amzn2023 ALAS2023-2026-3187

Azure Linux

ReleasePackageFixed inAdvisory
Azure Linux 3 kernel 6.6.161.1-1 —

Oracle Linux

ReleasePackageFixed inAdvisory
Oracle Linux 10 rv +29 6.12.0-211.69.1.el10_2 ELSA-2026-91565
Oracle Linux 9 rv +28 5.14.0-687.61.1.el9_8 ELSA-2026-90365
Oracle Linux 8 perf +19 4.18.0-553.178.1.el8_10 ELSA-2026-89083

Advisories 43

References