Unscored CVE-2026-52944 EUVD-2026-38734GHSA-v762-vr2v-9263

ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE

Published Jun 24, 2026 · Updated Sep 14, 2026 · Assigned by Linux

Vendor: Linux Product: Linux 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-5.8 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-fips Package: linux-azure 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-5.8 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-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-5.8 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-5.8 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-6.8 Package: linux-intel-5.13 Package: linux-intel-iot-realtime Package: linux-intel-iotg Package: linux-intel-iotg-5.15 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-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-5.8 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-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: Debian Ecosystem: Ubuntu

Description

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

ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE

FSCTL_SET_SPARSE in fsctl_set_sparse() modifies the file's sparse
attribute and saves it through xattr without any permission checks.

This exposes two issues:

1) A client on a read-only share can change the sparse attribute
on files it opened, even though the share is read-only.
Other FSCTL write operations already check
test_tree_conn_flag(work->tcon, KSMBD_TREE_CONN_FLAG_WRITABLE),
but FSCTL_SET_SPARSE does not.

2) Even on writable shares, clients without FILE_WRITE_DATA or
FILE_WRITE_ATTRIBUTES access should not modify the sparse
attribute. Similar handle-level checks exist in other functions
but are missing here.

Add both share-level writable check and per-handle access check.
Use goto out on error to avoid leaking file references.

Affected products

Vendor	Product	Affected	Fixed
Linux	Linux	5.15	5.15.221

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.

Debian

Security tracker ↗

Release	Package	Fixed in	Advisory
Debian 14	linux	7.0.12-1	—
Debian 13	linux	6.12.111-1	—
Debian 12	linux	6.1.190-1	—
Debian 12	linux-6.12	6.12.111-1~deb12u1	—

Ubuntu

Security tracker ↗

Release	Package	Fixed in	Advisory
Ubuntu Nvidia-BlueField 24.04 LTS	linux-bluefield	6.8.0-1032.37	—
Ubuntu Nvidia-BlueField 22.04 LTS	linux-bluefield	5.15.0-1103.105	—
Ubuntu 26.04 LTS	linux	7.0.0-28.28	USN-8566-1
Ubuntu 26.04 LTS	linux-aws +2	7.0.0-1009.9	USN-8618-1, USN-8603-1, USN-8568-1
Ubuntu 26.04 LTS	linux-gcp +1	7.0.0-1008.8	USN-8593-1, USN-8566-1
Ubuntu 26.04 LTS	linux-gke	7.0.0-1003.4	USN-8566-1
Ubuntu 26.04 LTS	linux-ibm +1	7.0.0-1010.10	USN-8603-1, USN-8593-1
Ubuntu 26.04 LTS	linux-nvidia	7.0.0-1016.16	USN-8663-1
Ubuntu 26.04 LTS	linux-nvidia-bos	7.0.0-2016.16	USN-8664-1
Ubuntu 26.04 LTS	linux-raspi	7.0.0-1015.15	USN-8618-1
Ubuntu 26.04 LTS	linux-riscv +1	7.0.0-28.28.1	USN-8566-1
Ubuntu 25.10	linux +8	No fix yet	—
Ubuntu 24.04 LTS	linux	6.8.0-146.146	USN-8903-1
Ubuntu 24.04 LTS	linux-aws	6.8.0-1066.69	USN-8903-1
Ubuntu 24.04 LTS	linux-azure-7.0	7.0.0-1014.14~24.04.1	USN-8728-2
Ubuntu 24.04 LTS	linux-azure-fde	6.8.0-1068.75	USN-8904-1
Ubuntu 24.04 LTS	linux-azure-fde-7.0	7.0.0-1013.13~24.04.1	—
Ubuntu 24.04 LTS	linux-gcp +1	6.8.0-1070.78	USN-8905-2, USN-8904-1
Ubuntu 24.04 LTS	linux-gcp-7.0 +1	7.0.0-1011.11~24.04.1	USN-8728-3, USN-8728-1
Ubuntu 24.04 LTS	linux-gke	6.8.0-1065.73	USN-8903-2
Ubuntu 24.04 LTS	linux-gkeop	6.8.0-1051.55	USN-8903-2
Ubuntu 24.04 LTS	linux-hwe-7.0	7.0.0-28.28~24.04.1	USN-8569-1
Ubuntu 24.04 LTS	linux-ibm	6.8.0-1066.67	USN-8903-2
Ubuntu 24.04 LTS	linux-lowlatency	6.8.0-146.146.1	USN-8903-2
Ubuntu 24.04 LTS	linux-nvidia	6.8.0-1064.67	USN-8903-2
Ubuntu 24.04 LTS	linux-nvidia-7.0	7.0.0-1016.16~24.04.1	USN-8663-1
Ubuntu 24.04 LTS	linux-nvidia-lowlatency	6.8.0-1064.67.1	USN-8903-2
Ubuntu 24.04 LTS	linux-nvidia-tegra	6.8.0-1038.42	USN-9002-1
Ubuntu 24.04 LTS	linux-oracle	6.8.0-1063.66	USN-8903-2
Ubuntu 24.04 LTS	linux-raspi	6.8.0-1068.72	USN-9025-1
Ubuntu 24.04 LTS	linux-riscv +29	No fix yet	—
Ubuntu 24.04 LTS	linux-riscv-7.0	7.0.0-28.28.1~24.04.3	—
Ubuntu 24.04 LTS	linux-vmware	6.8.0-1008.8	—

Show 10 more (older releases, extended support, other products)

Release	Package	Fixed in	Advisory
Ubuntu 22.04 LTS	linux	5.15.0-202.212	USN-8961-1
Ubuntu 22.04 LTS	linux-aws	5.15.0-1119.126	USN-8961-1
Ubuntu 22.04 LTS	linux-aws-6.8	6.8.0-1066.69~22.04.1	USN-8903-1
Ubuntu 22.04 LTS	linux-azure	5.15.0-1125.134	USN-8961-1
Ubuntu 22.04 LTS	linux-azure-fde	5.15.0-1124.133	USN-8962-1
Ubuntu 22.04 LTS	linux-azure-fde-6.8	6.8.0-1068.75~22.04.1	USN-8904-1
Ubuntu 22.04 LTS	linux-gcp	5.15.0-1120.130	USN-8961-1
Ubuntu 22.04 LTS	linux-gcp-6.8 +1	6.8.0-1070.78~22.04.1	USN-8905-1, USN-8904-1
Ubuntu 22.04 LTS	linux-gke	5.15.0-1115.121	USN-8961-1
Ubuntu 22.04 LTS	linux-gkeop	5.15.0-1102.110	USN-8961-1
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	5.15.0-1113.117	USN-8961-1
Ubuntu 22.04 LTS	linux-ibm-6.8	6.8.0-1066.67~22.04.1	USN-8906-1
Ubuntu 22.04 LTS	linux-intel-iotg	5.15.0-1114.120	USN-8961-1
Ubuntu 22.04 LTS	linux-kvm	5.15.0-1111.116	USN-8961-1
Ubuntu 22.04 LTS	linux-lowlatency	5.15.0-197.207	USN-8961-1
Ubuntu 22.04 LTS	linux-lowlatency-hwe-6.8	6.8.0-146.146.1~22.04.1	USN-8903-2
Ubuntu 22.04 LTS	linux-nvidia	5.15.0-1114.115	USN-8961-1
Ubuntu 22.04 LTS	linux-nvidia-6.8	6.8.0-1064.67~22.04.1	USN-8903-2
Ubuntu 22.04 LTS	linux-nvidia-tegra	5.15.0-1070.72	USN-8963-1
Ubuntu 22.04 LTS	linux-nvidia-tegra-igx	5.15.0-1059.59	USN-8963-1
Ubuntu 22.04 LTS	linux-oracle	5.15.0-1116.122	USN-8961-1
Ubuntu 22.04 LTS	linux-oracle-6.8	6.8.0-1067.71~22.04.1	USN-9025-1
Ubuntu 22.04 LTS	linux-raspi	5.15.0-1113.116	USN-9029-1
Ubuntu 22.04 LTS	linux-riscv +33	No fix yet	—
Ubuntu 22.04 LTS	linux-riscv-6.8	6.8.0-146.146~22.04.1	—
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	6.8.1-1061.62	USN-8903-1
Ubuntu Pro Realtime 24.04 LTS	linux-realtime-6.14 +1	No fix yet	—
Ubuntu Pro Realtime 22.04 LTS	linux-intel-iot-realtime	5.15.0-1111.115	USN-8961-1
Ubuntu Pro Realtime 22.04 LTS	linux-realtime	5.15.0-1118.127	USN-8961-1
Ubuntu Pro Realtime 22.04 LTS	linux-realtime-6.8	6.8.1-1061.62~22.04.1	USN-8903-1
Ubuntu Pro FIPS-updates 24.04 LTS	linux-aws-fips	6.8.0-1066.69+fips1	USN-8903-1
Ubuntu Pro FIPS-updates 24.04 LTS	linux-azure-fips	6.8.0-1069.77+fips1	USN-8904-1
Ubuntu Pro FIPS-updates 24.04 LTS	linux-fips	6.8.0-146.146+fips1	USN-8903-1
Ubuntu Pro FIPS-updates 24.04 LTS	linux-gcp-fips	6.8.0-1070.78+fips1	USN-8905-1
Ubuntu Pro FIPS-updates 22.04 LTS	linux-aws-fips	5.15.0-1119.126+fips1	USN-8961-1
Ubuntu Pro FIPS-updates 22.04 LTS	linux-azure-fips	5.15.0-1125.134+fips1	USN-8961-1
Ubuntu Pro FIPS-updates 22.04 LTS	linux-fips	5.15.0-202.212+fips1	USN-8961-1
Ubuntu Pro FIPS-updates 22.04 LTS	linux-gcp-fips	5.15.0-1120.130+fips1	USN-8961-1
Ubuntu Pro FIPS-preview 22.04 LTS	linux-fips +3	No fix yet	—
Ubuntu Pro 20.04 LTS	linux-aws-5.15	5.15.0-1119.126~20.04.1	USN-8961-1
Ubuntu Pro 20.04 LTS	linux-azure-5.15	5.15.0-1125.134~20.04.1	USN-8961-1
Ubuntu Pro 20.04 LTS	linux-azure-fde-5.15	5.15.0-1124.133~20.04.1	USN-8961-1
Ubuntu Pro 20.04 LTS	linux-gcp-5.15	5.15.0-1120.130~20.04.1	USN-8961-1
Ubuntu Pro 20.04 LTS	linux-hwe-5.15	5.15.0-202.212~20.04.1	USN-8961-1
Ubuntu Pro 20.04 LTS	linux-ibm-5.15	5.15.0-1113.117~20.04.1	USN-8961-1
Ubuntu Pro 20.04 LTS	linux-intel-iotg-5.15	5.15.0-1114.120~20.04.1	USN-8961-1
Ubuntu Pro 20.04 LTS	linux-lowlatency-hwe-5.15	5.15.0-197.207~20.04.1	USN-8961-1
Ubuntu Pro 20.04 LTS	linux-nvidia-tegra-5.15	5.15.0-1070.72~20.04.1	USN-8963-1
Ubuntu Pro 20.04 LTS	linux-oracle-5.15	5.15.0-1116.122~20.04.1	USN-8961-1
Ubuntu Pro 20.04 LTS	linux-riscv-5.15	5.15.0-1113.117~20.04.2	—

Advisories 25

USN-9066-1 linux-hwe-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
WID-SEC-2026-2077 Linux Kernel: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 12, 2026
USN-8961-1 linux, linux-aws, linux-aws-5.15, linux-aws-fips, linux-azure, linux-azure-5.15, linux-azure-fde-5.15, linux-azure-fips, linux-fips, linux-gcp, linux-gcp-5.15, linux-gcp-fips, linux-gke, linux-gkeop, linux-hwe-5.15, linux-ibm, linux-ibm-5.15, linux-intel-iot-realtime, linux-intel-iotg, linux-intel-iotg-5.15, linux-kvm, linux-lowlatency, linux-lowlatency-hwe-5.15, linux-nvidia, linux-oracle, linux-oracle-5.15, linux-realtime vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-8963-1 linux-nvidia-tegra, linux-nvidia-tegra-5.15, linux-nvidia-tegra-igx vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-9025-1 linux-oracle-6.8, linux-raspi, linux-raspi-realtime vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-9029-1 linux-raspi vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-8962-1 linux-azure-fde vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-8728-1 linux-gcp-7.0 vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-8728-2 linux-azure-7.0 vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-9002-1 linux-nvidia-tegra vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-8728-3 linux-oracle-7.0 vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-8903-2 linux-gke, linux-gkeop, linux-ibm, linux-lowlatency, linux-lowlatency-hwe-6.8, linux-nvidia, linux-nvidia-6.8, linux-nvidia-lowlatency, linux-oracle vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
USN-8903-1 linux, linux-aws, linux-aws-6.8, linux-aws-fips, linux-fips, linux-realtime, linux-realtime-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
USN-8904-1 linux-azure, linux-azure-6.8, linux-azure-fde, linux-azure-fde-6.8, linux-azure-fips vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
USN-8905-2 linux-gcp vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
USN-8905-1 linux-gcp-6.8, linux-gcp-fips vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
USN-8906-1 linux-ibm-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
USN-8593-1 linux-ibm, linux-oracle vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
USN-8664-1 linux-nvidia-bos vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
USN-8603-1 linux-azure, linux-azure-fde vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
USN-8663-1 linux-nvidia, linux-nvidia-7.0 vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
USN-8618-1 linux-aws, linux-raspi vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026
USN-8566-1 linux, linux-gcp, linux-gke, linux-realtime vulnerabilities Ubuntu Security Notices (USN) · Nov 7, 2026
USN-8569-1 linux-hwe-7.0 vulnerabilities Ubuntu Security Notices (USN) · Nov 7, 2026
USN-8568-1 linux-oem-7.0 vulnerabilities Ubuntu Security Notices (USN) · Nov 7, 2026

References