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Critical · 9.8 CVE-2026-43185 EUVD-2026-27748GHSA-vcg7-gx5w-x44c

ksmbd: fix signededness bug in smb_direct_prepare_negotiation()

Published May 6, 2026 · Updated Oct 30, 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-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-6.2 Package: linux-azure-fde-6.8 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-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-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-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-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-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-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 signededness bug in smb_direct_prepare_negotiation()

smb_direct_prepare_negotiation() casts an unsigned __u32 value
from sp->max_recv_size and req->preferred_send_size to a signed
int before computing min_t(int, ...). A maliciously provided
preferred_send_size of 0x80000000 will return as smaller than
max_recv_size, and then be used to set the maximum allowed
alowed receive size for the next message.

By sending a second message with a large value (>1420 bytes)
the attacker can then achieve a heap buffer overflow.

This fix replaces min_t(int, ...) with min_t(u32)

Affected products

VendorProductAffectedFixed
Linux Linux 5.15 6.1.191

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 ↗
ReleasePackageFixed inAdvisory
Debian 14 linux 6.19.6-1 —
Debian 13 linux 6.12.115-2 —
Debian 12 linux No fix yet —
Debian 12 linux-6.12 6.12.115-2~deb12u1 —

Ubuntu

Security tracker ↗
ReleasePackageFixed inAdvisory
Ubuntu Nvidia-BlueField 24.04 LTS linux-bluefield 6.8.0-1026.30 —
Ubuntu Nvidia-BlueField 22.04 LTS linux-bluefield 5.15.0-1095.97 —
Ubuntu 25.10 linux +7 No fix yet —
Ubuntu 25.10 linux-raspi 6.17.0-1021.21 USN-8546-1
Ubuntu 24.04 LTS linux 6.8.0-134.134 —
Ubuntu 24.04 LTS linux-aws 6.8.0-1060.63 —
Ubuntu 24.04 LTS linux-azure 6.8.0-1063.71 USN-8606-1
Ubuntu 24.04 LTS linux-azure-6.17 6.17.0-1021.21~24.04.1 USN-8604-1
Ubuntu 24.04 LTS linux-azure-fde 6.8.0-1062.69 USN-8607-1
Ubuntu 24.04 LTS linux-gcp 6.8.0-1063.69 —
Ubuntu 24.04 LTS linux-gcp-6.17 6.17.0-1020.22~24.04.1 —
Ubuntu 24.04 LTS linux-gke 6.8.0-1058.64 —
Ubuntu 24.04 LTS linux-gkeop 6.8.0-1045.48 —
Ubuntu 24.04 LTS linux-hwe-6.17 6.17.0-40.40~24.04.1 USN-8545-1
Ubuntu 24.04 LTS linux-ibm 6.8.0-1060.61 —
Ubuntu 24.04 LTS linux-lowlatency 6.8.0-134.134.1 —
Ubuntu 24.04 LTS linux-nvidia 6.8.0-1058.61 —
Ubuntu 24.04 LTS linux-nvidia-6.17 6.17.0-1026.26 —
Ubuntu 24.04 LTS linux-nvidia-lowlatency 6.8.0-1058.61.1 —
Ubuntu 24.04 LTS linux-nvidia-tegra 6.8.0-1029.30 —
Ubuntu 24.04 LTS linux-oem-6.17 6.17.0-1028.28 —
Ubuntu 24.04 LTS linux-oracle 6.8.0-1057.58 —
Ubuntu 24.04 LTS linux-oracle-6.17 +1 6.17.0-1018.18~24.04.1 USN-8605-1
Ubuntu 24.04 LTS linux-raspi 6.8.0-1060.64 —
Ubuntu 24.04 LTS linux-riscv +21 No fix yet —
Ubuntu 24.04 LTS linux-vmware 6.8.0-1008.8 —
Ubuntu 24.04 LTS linux-xilinx 6.8.0-1032.33 —
Ubuntu 22.04 LTS linux 5.15.0-185.195 —
Ubuntu 22.04 LTS linux-aws 5.15.0-1111.118 —
Ubuntu 22.04 LTS linux-aws-6.8 6.8.0-1060.63~22.04.1 —
Ubuntu 22.04 LTS linux-azure +1 5.15.0-1116.125 —
Ubuntu 22.04 LTS linux-azure-6.8 6.8.0-1063.71~22.04.1 USN-8606-1
Ubuntu 22.04 LTS linux-azure-fde-6.8 6.8.0-1062.69~22.04.1 USN-8609-1
Ubuntu 22.04 LTS linux-gcp 5.15.0-1111.121 —
Ubuntu 22.04 LTS linux-gcp-6.8 6.8.0-1063.69~22.04.1 —
Ubuntu 22.04 LTS linux-gke 5.15.0-1107.113 —
Ubuntu 22.04 LTS linux-gkeop 5.15.0-1094.102 —
Ubuntu 22.04 LTS linux-hwe-6.8 6.8.0-136.136~22.04.1 USN-8619-1
Ubuntu 22.04 LTS linux-ibm 5.15.0-1105.109 —
Ubuntu 22.04 LTS linux-ibm-6.8 6.8.0-1060.61~22.04.1 —
Ubuntu 22.04 LTS linux-intel-iotg 5.15.0-1106.112 —
Ubuntu 22.04 LTS linux-kvm 5.15.0-1103.108 —
Ubuntu 22.04 LTS linux-lowlatency 5.15.0-183.193 —
Ubuntu 22.04 LTS linux-lowlatency-hwe-6.8 6.8.0-134.134.1~22.04.1 —
Ubuntu 22.04 LTS linux-nvidia 5.15.0-1106.107 —
Ubuntu 22.04 LTS linux-nvidia-6.8 6.8.0-1058.61~22.04.1 —
Ubuntu 22.04 LTS linux-nvidia-tegra 5.15.0-1063.63 —
Ubuntu 22.04 LTS linux-nvidia-tegra-igx 5.15.0-1052.52 —
Ubuntu 22.04 LTS linux-oracle 5.15.0-1108.114 —
Ubuntu 22.04 LTS linux-oracle-6.8 6.8.0-1057.58~22.04.1 —
Ubuntu 22.04 LTS linux-raspi 5.15.0-1105.108 —
Ubuntu 22.04 LTS linux-riscv +32 No fix yet —
Ubuntu 22.04 LTS linux-riscv-6.8 6.8.0-134.134~22.04.1 —
Ubuntu 22.04 LTS linux-xilinx-zynqmp 5.15.0-1074.78 —
Show 14 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 6.8.0-2049.50 —
Ubuntu Pro Realtime 24.04 LTS linux-realtime 6.8.1-1055.56 —
Ubuntu Pro Realtime 24.04 LTS linux-realtime-6.14 No fix yet —
Ubuntu Pro Realtime 24.04 LTS linux-realtime-6.17 6.17.0-1017.19~24.04.1 —
Ubuntu Pro Realtime 22.04 LTS linux-intel-iot-realtime 5.15.0-1103.105 —
Ubuntu Pro Realtime 22.04 LTS linux-realtime 5.15.0-1110.119 —
Ubuntu Pro Realtime 22.04 LTS linux-realtime-6.8 6.8.1-1055.56~22.04.1 —
Ubuntu Pro FIPS-updates 24.04 LTS linux-aws-fips 6.8.0-1060.63+fips1 —
Ubuntu Pro FIPS-updates 24.04 LTS linux-azure-fips 6.8.0-1062.69+fips1 —
Ubuntu Pro FIPS-updates 24.04 LTS linux-fips 6.8.0-134.134+fips1 —
Ubuntu Pro FIPS-updates 24.04 LTS linux-gcp-fips 6.8.0-1063.69+fips1 —
Ubuntu Pro FIPS-updates 22.04 LTS linux-aws-fips 5.15.0-1111.118+fips1 —
Ubuntu Pro FIPS-updates 22.04 LTS linux-azure-fips 5.15.0-1116.125+fips1 USN-8547-2
Ubuntu Pro FIPS-updates 22.04 LTS linux-fips 5.15.0-185.195+fips1 —
Ubuntu Pro FIPS-updates 22.04 LTS linux-gcp-fips 5.15.0-1111.121+fips1 —
Ubuntu Pro FIPS-preview 22.04 LTS linux-fips +3 No fix yet —
Ubuntu Pro 26.04 LTS linux 7.0.0-28.28 LSN-0121-1
Ubuntu Pro 26.04 LTS linux-aws 7.0.0-1009.9 LSN-0121-1
Ubuntu Pro 26.04 LTS linux-azure 7.0.0-1010.10 LSN-0121-1
Ubuntu Pro 26.04 LTS linux-gcp 7.0.0-1008.8 LSN-0121-1
Ubuntu Pro 24.04 LTS linux 6.8.0-136.136 LSN-0121-1
Ubuntu Pro 24.04 LTS linux-aws 6.8.0-1061.64 LSN-0121-1
Ubuntu Pro 24.04 LTS linux-azure 6.8.0-1063.71 LSN-0121-1
Ubuntu Pro 24.04 LTS linux-gcp 6.8.0-1064.72 LSN-0121-1
Ubuntu Pro 24.04 LTS linux-gke 6.8.0-1059.67 LSN-0121-1
Ubuntu Pro 24.04 LTS linux-ibm 6.8.0-1061.62 LSN-0121-1
Ubuntu Pro 24.04 LTS linux-oracle 6.8.0-1058.61 LSN-0121-1
Ubuntu Pro 22.04 LTS linux 5.15.0-187.197 LSN-0121-1
Ubuntu Pro 22.04 LTS linux-aws 5.15.0-1113.120 LSN-0121-1
Ubuntu Pro 22.04 LTS linux-aws-6.8 6.8.0-1061.64~22.04.1 LSN-0121-1
Ubuntu Pro 22.04 LTS linux-azure 5.15.0-1118.127 LSN-0121-1
Ubuntu Pro 22.04 LTS linux-gcp 5.15.0-1114.124 LSN-0121-1
Ubuntu Pro 22.04 LTS linux-gcp-6.8 6.8.0-1064.72~22.04.1 LSN-0121-1
Ubuntu Pro 22.04 LTS linux-gke 5.15.0-1110.116 LSN-0121-1
Ubuntu Pro 22.04 LTS linux-hwe-6.8 6.8.0-136.136~22.04.1 LSN-0121-1
Ubuntu Pro 22.04 LTS linux-ibm 5.15.0-1107.111 LSN-0121-1
Ubuntu Pro 22.04 LTS linux-ibm-6.8 6.8.0-1061.62~22.04.1 LSN-0121-1
Ubuntu Pro 20.04 LTS linux 5.4.0-234.254 LSN-0121-1
Ubuntu Pro 20.04 LTS linux-aws-5.15 5.15.0-1111.118~20.04.1 —
Ubuntu Pro 20.04 LTS linux-azure-5.15 +1 5.15.0-1116.125~20.04.1 —
Ubuntu Pro 20.04 LTS linux-gcp-5.15 5.15.0-1111.121~20.04.1 USN-8547-1
Ubuntu Pro 20.04 LTS linux-hwe-5.15 5.15.0-185.195~20.04.1 —
Ubuntu Pro 20.04 LTS linux-ibm-5.15 +1 5.15.0-1105.109~20.04.1 —
Ubuntu Pro 20.04 LTS linux-intel-iotg-5.15 5.15.0-1106.112~20.04.1 USN-8547-1
Ubuntu Pro 20.04 LTS linux-lowlatency-hwe-5.15 5.15.0-183.193~20.04.1 —
Ubuntu Pro 20.04 LTS linux-nvidia-tegra-5.15 5.15.0-1063.63~20.04.1 —
Ubuntu Pro 20.04 LTS linux-oracle-5.15 5.15.0-1108.114~20.04.1 —
Ubuntu Pro 18.04 LTS linux 4.15.0-254.266 LSN-0121-1
Ubuntu Pro 18.04 LTS linux-aws 4.15.0-1195.208 LSN-0121-1
Ubuntu Pro 18.04 LTS linux-azure-4.15 4.15.0-1205.220 LSN-0121-1
Ubuntu Pro 18.04 LTS linux-gcp-4.15 4.15.0-1188.205 LSN-0121-1
Ubuntu Pro 18.04 LTS linux-hwe-5.4 5.4.0-234.254~18.04.1 LSN-0121-1
Ubuntu Pro 18.04 LTS linux-oracle 4.15.0-1158.169 LSN-0121-1
Ubuntu Pro 16.04 LTS linux 4.4.0-284.318 LSN-0121-1
Ubuntu Pro 16.04 LTS linux-aws 4.4.0-1195.210 LSN-0121-1
Ubuntu Pro 16.04 LTS linux-aws-hwe 4.15.0-1195.208~16.04.1 LSN-0121-1
Ubuntu Pro 16.04 LTS linux-azure 4.15.0-1205.220~16.04.1 LSN-0121-1
Ubuntu Pro 16.04 LTS linux-gcp 4.15.0-1188.205~16.04.1 LSN-0121-1
Ubuntu Pro 16.04 LTS linux-hwe 4.15.0-254.266~16.04.1 LSN-0121-1

Advisories 12

References