Critical · 9.1 CVE-2026-68431 EUVD-2026-57039GHSA-6pm5-g7cv-g948

ksmbd: validate minimum PDU size for transform requests

Published Aug 12, 2026 · Updated Aug 23, 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: validate minimum PDU size for transform requests

The receive path applies the minimum SMB2 PDU size check only when
ProtocolId is SMB2_PROTO_NUMBER. A packet carrying
SMB2_TRANSFORM_PROTO_NUM bypasses the check even when the negotiated
dialect does not provide transform handling.

On an SMB 2.1 connection, a short transform packet therefore reaches
init_smb2_rsp_hdr(), which interprets the request as a full SMB2 header
and reads beyond the request allocation. The copied fields can then be
returned to the unauthenticated client.

Compression transforms are converted to ordinary SMB2 messages before
protocol validation. After that conversion, validate ordinary SMB2
requests against SMB2_MIN_SUPPORTED_PDU_SIZE and require encryption
transform requests to contain both a transform header and an SMB2
header. This rejects truncated requests before work allocation.

Affected products

Vendor	Product	Affected	Fixed
Linux	Linux	5.15.145 – < 5.15.217, 6.1.34 – < 6.1.184, 6.3.8 – < 6.4, 6.4	5.15.217

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	7.1.6-1	—
Debian 13	linux	6.12.105-1	—
Debian 12	linux	6.1.187-1	—
Debian 12	linux-6.12	6.12.107-1~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	5.15.0-1103.105	—
Ubuntu 26.04 LTS	linux	7.0.0-38.38	USN-8887-1
Ubuntu 26.04 LTS	linux-aws +1	7.0.0-1014.14	USN-8887-1
Ubuntu 26.04 LTS	linux-azure	7.0.0-1017.17	USN-8888-1
Ubuntu 26.04 LTS	linux-azure-fde	7.0.0-1016.16	USN-8888-1
Ubuntu 26.04 LTS	linux-gke	7.0.0-1008.9	USN-8887-1
Ubuntu 26.04 LTS	linux-ibm +1	7.0.0-1015.15	USN-8889-1, USN-8887-1
Ubuntu 26.04 LTS	linux-nvidia	7.0.0-1025.26	USN-9043-1
Ubuntu 26.04 LTS	linux-nvidia-bos	7.0.0-2022.23	USN-9003-1
Ubuntu 26.04 LTS	linux-oracle	7.0.0-1013.13	USN-8887-1
Ubuntu 26.04 LTS	linux-raspi	7.0.0-1023.23	USN-9021-1
Ubuntu 26.04 LTS	linux-riscv +1	7.0.0-38.38.1	USN-8887-1
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 +1	7.0.0-1014.14~24.04.1	USN-8887-3, USN-8887-2
Ubuntu 24.04 LTS	linux-azure	6.8.0-1073.82	USN-9022-1
Ubuntu 24.04 LTS	linux-azure-7.0	7.0.0-1017.17~24.04.1	USN-8888-2
Ubuntu 24.04 LTS	linux-azure-fde	6.8.0-1071.78	USN-9039-1
Ubuntu 24.04 LTS	linux-azure-fde-7.0	7.0.0-1016.16~24.04.1	USN-8888-2
Ubuntu 24.04 LTS	linux-gcp	6.8.0-1073.81	USN-9022-1
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	7.0.0-38.38~24.04.4	USN-8887-3
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-7.0	7.0.0-1024.25~24.04.1	USN-9003-1
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	7.0.0-1013.13~24.04.1	USN-8887-3
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	7.0.0-38.38.1~24.04.1	—
Ubuntu 24.04 LTS	linux-vmware	6.8.0-1010.10	USN-9022-1
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	6.8.0-1069.74~22.04.1	USN-9024-1
Ubuntu 22.04 LTS	linux-azure	5.15.0-1125.134	USN-8961-1
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	5.15.0-1124.133	—
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	5.15.0-1120.130	USN-8961-1
Ubuntu 22.04 LTS	linux-gcp-6.8	6.8.0-1073.81~22.04.1	USN-9024-1
Ubuntu 22.04 LTS	linux-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	6.8.0-1069.70~22.04.1	USN-9024-1
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	6.8.0-149.149.1~22.04.1	USN-9024-1
Ubuntu 22.04 LTS	linux-nvidia	5.15.0-1114.115	USN-8961-1
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 +34	No fix yet	—

Show 8 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-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	6.8.1-1064.65~22.04.1	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-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 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 22

USN-9066-1 linux-hwe-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-9021-1 linux-raspi vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 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 12, 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 12, 2026
USN-9026-1 linux-azure-6.8, linux-azure-fde-6.8 vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-9039-1 linux-azure-fde vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
WID-SEC-2026-2799 Linux Kernel: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff BSI CERT-Bund (WID) · Nov 12, 2026
USN-9040-1 linux-nvidia-lowlatency vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-9043-1 linux-nvidia vulnerabilities Ubuntu Security Notices (USN) · 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-9023-1 linux-aws-fips, linux-gcp-fips, linux-gkeop, linux-realtime vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-8887-1 linux, linux-aws, linux-gcp, linux-gke, linux-ibm, linux-oracle, linux-realtime vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-9029-1 linux-raspi vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-9003-1 linux-nvidia-7.0, linux-nvidia-bos vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-8887-3 linux-gcp-7.0, linux-hwe-7.0, linux-oracle-7.0 vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-8888-2 linux-azure-7.0, linux-azure-fde-7.0 vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-8888-1 linux-azure, linux-azure-fde vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-8887-2 linux-aws-7.0 vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-8889-1 linux-oem-7.0 vulnerabilities Ubuntu Security Notices (USN) · Nov 12, 2026
USN-8781-1 linux-nvidia-tegra vulnerabilities Ubuntu Security Notices (USN) · Nov 9, 2026

References