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Vulnerability · Published Apr 22, 2026 · Assigned by Linux

CVE-2026-31478ksmbd: replace hardcoded hdr2_len with offsetof() in smb2_calc_max_out_buf_len()

Critical 9.8

In plain English

A critical-severity security flaw in Linux from Linux. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 43% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)9.8Critical
Exploit odds (30 days)0.5%top 56.8% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: replace hardcoded hdr2_len with offsetof() in smb2_calc_max_out_buf_len() After this commit (e2b76ab8b5c9 "ksmbd: add support for read compound"), response buffer management was changed to use dynamic iov array. In the new design, smb2_calc_max_out_buf_len() expects the second argument (hdr2_len) to be the offset of ->Buffer field in the response structure, not a hardcoded magic number. Fix the remaining call sites to use the correct offsetof() value.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12linux6.1.170-1DEBIAN-CVE-2026-31478
Debian:13linux6.12.85-1DEBIAN-CVE-2026-31478
Debian:14linux6.19.11-1DEBIAN-CVE-2026-31478
Ubuntu:22.04:LTSlinux5.15.0-185.195UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux5.15.0-185.195USN-8493-1
Ubuntu:24.04:LTSlinux6.8.0-134.134UBUNTU-CVE-2026-31478
Ubuntu:25.10linux6.17.0-40.40UBUNTU-CVE-2026-31478
Ubuntu:25.10linux6.17.0-40.40USN-8490-1
Ubuntu:22.04:LTSlinux-allwinner-5.19no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-aws5.15.0-1111.118UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-aws5.15.0-1111.118USN-8493-1
Ubuntu:24.04:LTSlinux-aws6.8.0-1060.63UBUNTU-CVE-2026-31478
Ubuntu:25.10linux-aws6.17.0-1019.19UBUNTU-CVE-2026-31478
Ubuntu:25.10linux-aws6.17.0-1019.19USN-8490-1
Ubuntu:22.04:LTSlinux-aws-5.19no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-aws-6.14no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-aws-6.176.17.0-1019.19~24.04.1UBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-aws-6.176.17.0-1019.19~24.04.1USN-8490-1
Ubuntu:22.04:LTSlinux-aws-6.2no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-aws-6.5no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-aws-6.86.8.0-1060.63~22.04.1UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-azure5.15.0-1116.125UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-azure5.15.0-1116.125USN-8493-1
Ubuntu:24.04:LTSlinux-azure6.8.0-1063.71UBUNTU-CVE-2026-31478
Ubuntu:25.10linux-azureno fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-azure-5.19no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-azure-6.11no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-azure-6.14no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-azure-6.176.17.0-1021.21~24.04.1UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-azure-6.2no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-azure-6.5no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-azure-6.86.8.0-1063.71~22.04.1UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-azure-fde5.15.0-1116.125UBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-azure-fde6.8.0-1062.69UBUNTU-CVE-2026-31478
Ubuntu:25.10linux-azure-fdeno fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-azure-fde-5.19no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-azure-fde-6.14no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-azure-fde-6.2no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-azure-fde-6.86.8.0-1062.69~22.04.1UBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-azure-nvidiano fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-azure-nvidia-6.14no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-gcp5.15.0-1111.121UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-gcp5.15.0-1111.121USN-8493-1
Ubuntu:24.04:LTSlinux-gcp6.8.0-1063.69UBUNTU-CVE-2026-31478
Ubuntu:25.10linux-gcp6.17.0-1020.22UBUNTU-CVE-2026-31478
Ubuntu:25.10linux-gcp6.17.0-1020.22USN-8490-1
Ubuntu:22.04:LTSlinux-gcp-5.19no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-gcp-6.11no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-gcp-6.14no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-gcp-6.176.17.0-1020.22~24.04.1UBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-gcp-6.176.17.0-1020.22~24.04.1USN-8490-1
Ubuntu:22.04:LTSlinux-gcp-6.2no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-gcp-6.5no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-gcp-6.86.8.0-1063.69~22.04.1UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-gke5.15.0-1107.113UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-gke5.15.0-1107.113USN-8493-1
Ubuntu:24.04:LTSlinux-gke6.8.0-1058.64UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-gkeop5.15.0-1094.102UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-gkeop5.15.0-1094.102USN-8493-1
Ubuntu:24.04:LTSlinux-gkeop6.8.0-1045.48UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-hwe-5.19no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-hwe-6.11no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-hwe-6.14no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-hwe-6.176.17.0-40.40~24.04.1USN-8545-1
Ubuntu:24.04:LTSlinux-hwe-6.176.17.0-40.40~24.04.1UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-hwe-6.2no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-hwe-6.5no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-hwe-6.86.8.0-136.136~22.04.1UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-ibm5.15.0-1105.109USN-8493-1
Ubuntu:22.04:LTSlinux-ibm5.15.0-1105.109UBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-ibm6.8.0-1060.61UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-ibm-6.86.8.0-1060.61~22.04.1UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-intel-iot-realtimeno fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-intel-iotg5.15.0-1106.112USN-8493-1
Ubuntu:22.04:LTSlinux-intel-iotg5.15.0-1106.112UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-kvm5.15.0-1103.108USN-8493-1
Ubuntu:22.04:LTSlinux-kvm5.15.0-1103.108UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-lowlatency5.15.0-183.193USN-8493-1
Ubuntu:22.04:LTSlinux-lowlatency5.15.0-183.193UBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-lowlatency6.8.0-134.134.1UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-lowlatency-hwe-5.19no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-lowlatency-hwe-6.11no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-lowlatency-hwe-6.2no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-lowlatency-hwe-6.5no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-lowlatency-hwe-6.86.8.0-134.134.1~22.04.1UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-nvidia5.15.0-1106.107USN-8493-1
Ubuntu:22.04:LTSlinux-nvidia5.15.0-1106.107UBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-nvidia6.8.0-1058.61UBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-nvidia-6.11no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-nvidia-6.176.17.0-1026.26UBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-nvidia-6.176.17.0-1026.26USN-8508-1
Ubuntu:22.04:LTSlinux-nvidia-6.2no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-nvidia-6.5no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-nvidia-6.86.8.0-1058.61~22.04.1UBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-nvidia-lowlatency6.8.0-1058.61.1UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-nvidia-tegra5.15.0-1063.63UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-nvidia-tegra5.15.0-1063.63USN-8493-1
Ubuntu:24.04:LTSlinux-nvidia-tegra6.8.0-1029.30UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-nvidia-tegra-igx5.15.0-1052.52UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-nvidia-tegra-igx5.15.0-1052.52USN-8493-1
Ubuntu:22.04:LTSlinux-oem-5.17no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-oem-6.0no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-oem-6.1no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-oem-6.11no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-oem-6.14no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-oem-6.176.17.0-1028.28UBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-oem-6.176.17.0-1028.28USN-8491-1
Ubuntu:22.04:LTSlinux-oem-6.5no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-oem-6.8no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-oracle5.15.0-1108.114UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-oracle5.15.0-1108.114USN-8493-1
Ubuntu:24.04:LTSlinux-oracle6.8.0-1057.58UBUNTU-CVE-2026-31478
Ubuntu:25.10linux-oracle6.17.0-1018.18UBUNTU-CVE-2026-31478
Ubuntu:25.10linux-oracle6.17.0-1018.18USN-8490-1
Ubuntu:24.04:LTSlinux-oracle-6.14no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-oracle-6.176.17.0-1018.18~24.04.1USN-8490-1
Ubuntu:24.04:LTSlinux-oracle-6.176.17.0-1018.18~24.04.1UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-oracle-6.5no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-oracle-6.86.8.0-1057.58~22.04.1UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-raspi5.15.0-1105.108USN-8527-1
Ubuntu:22.04:LTSlinux-raspi5.15.0-1105.108UBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-raspi6.8.0-1060.64UBUNTU-CVE-2026-31478
Ubuntu:25.10linux-raspi6.17.0-1021.21USN-8546-1
Ubuntu:25.10linux-raspi6.17.0-1021.21UBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-raspi-realtimeno fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-realtimeno fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-realtimeno fix listedUBUNTU-CVE-2026-31478
Ubuntu:25.10linux-realtime6.17.0-1017.19USN-8490-2
Ubuntu:25.10linux-realtime6.17.0-1017.19UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-riscvno fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-riscvno fix listedUBUNTU-CVE-2026-31478
Ubuntu:25.10linux-riscv6.17.0-40.40.1UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-riscv-5.19no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-riscv-6.14no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-riscv-6.17no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-riscv-6.5no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-riscv-6.86.8.0-134.134~22.04.1UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-starfive-5.19no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-starfive-6.2no fix listedUBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-starfive-6.5no fix listedUBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-vmware6.8.0-1008.8UBUNTU-CVE-2026-31478
Ubuntu:24.04:LTSlinux-xilinx6.8.0-1032.33UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-xilinx-zynqmp5.15.0-1074.78UBUNTU-CVE-2026-31478
Ubuntu:22.04:LTSlinux-xilinx-zynqmp5.15.0-1074.78USN-8528-1

Affected products (as reported)

VendorProductVersions
Linux Linux f2283680a80571ca82d710bc6ecd8f8beac67d63 – before 70b4c414889492c522b6e4331562360f49be23619f297df20d93411c0b4ddad7f88ba04a7cd36e77 – before 9a7166f0ef8cbb7bb48dd05e2471d995566003f5e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d – before c3a89e3ec1ccf64fa6a34e391e1581ebbcba8683e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d – before 6aef1765d6807e0f027cd87f6ac973eb0879a46de2b76ab8b5c9327ab2dae6da05d0752eb2f4771d – before 80824c7e527b70cf9039534e60aff592e8f209d1e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d – before 4cb537ae4f37d7d0f617815ed4bed7173fb50861e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d – before 0e55f63dd08f09651d39e1b709a91705a8a0ddcb5.15.145 – before 5.15.203
Linux Linux 6.6

Weakness: CWE-131 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References