Critical · 9.1 CVE-2026-74521 EUVD-2026-59714GHSA-336h-563m-gwm9

ksmbd: use memcmp() to compare ClientGUIDs

Published Aug 15, 2026 · Updated Oct 3, 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-7.0 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: use memcmp() to compare ClientGUIDs

ClientGUID is a fixed-size binary value and can contain embedded NUL
bytes. strncmp() stops comparing at the first NUL byte, so different
ClientGUID values can incorrectly be treated as equal.

Use memcmp() in SMB3 multichannel session binding and
FSCTL_VALIDATE_NEGOTIATE_INFO to compare all SMB2_CLIENT_GUID_SIZE
bytes.

Affected products

Vendor	Product	Affected	Fixed
Linux	Linux	5.15	6.1.189

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	7.1.8-1	—
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	6.8.0-1036.41	—
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	6.8.0-1035.38	USN-8781-1
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

Show 9 more (older releases, extended support, other products)

Release	Package	Fixed in	Advisory
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-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-preview 22.04 LTS	linux-fips +3	No fix yet	—
Ubuntu Pro 20.04 LTS	linux-aws-5.15 +10	No fix yet	—

Advisories 15

USN-9020-1 linux-aws-7.0, linux-azure-fde, linux-azure-fde-7.0, linux-gcp-7.0, linux-gke, linux-oracle-7.0, linux-realtime vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
USN-8959-1 linux, linux-aws, linux-gcp, linux-hwe-7.0, linux-ibm, linux-oracle vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
USN-9022-1 linux, linux-aws, linux-azure, linux-azure-fips, linux-gcp, linux-gke, linux-ibm, linux-lowlatency, linux-oracle, linux-vmware vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
USN-9025-1 linux-oracle-6.8, linux-raspi, linux-raspi-realtime vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
USN-9024-1 linux-aws-6.8, linux-gcp-6.8, linux-ibm-6.8, linux-lowlatency-hwe-6.8, linux-nvidia, linux-realtime-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
USN-9023-1 linux-aws-fips, linux-gcp-fips, linux-gkeop, linux-realtime vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
USN-9026-1 linux-azure-6.8, linux-azure-fde-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
USN-9021-1 linux-raspi vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
USN-9039-1 linux-azure-fde vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
USN-9040-1 linux-nvidia-lowlatency vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
USN-9066-1 linux-hwe-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
USN-9019-1 linux-azure vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
USN-8960-1 linux-oem-7.0 vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
WID-SEC-2026-2852 Linux Kernel: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 12, 2026
USN-8781-1 linux-nvidia-tegra vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026

References