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Linux Kernel: Unauthenticated SMB2 Requests Can Cause High CPU Usage

UBUNTU-CVE-2026-23220
Summary

A bug in the Linux kernel can cause high CPU usage and fill system logs with error messages when an unauthenticated SMB2 request is received. This happens when the kernel tries to process a request that has a bad signature. To fix this, the kernel has been updated to stop processing the request immediately, preventing the loop and the resulting issues. If you're using the Linux kernel, you should update to the latest version to ensure this issue is resolved.

What to do

No fix is available yet. Check with your software vendor for updates.

Affected software
VendorProductAffected versionsFix available
canonical linux All versions
canonical linux-aws All versions
canonical linux-azure All versions
canonical linux-lts-xenial All versions
canonical linux All versions
canonical linux-aws All versions
canonical linux-aws-hwe All versions
canonical linux-azure All versions
canonical linux-gcp All versions
canonical linux-hwe All versions
canonical linux-hwe-edge All versions
canonical linux-kvm All versions
canonical linux-oracle All versions
canonical linux-fips All versions
canonical linux-fips All versions
canonical linux All versions
canonical linux-aws All versions
canonical linux-aws-5.0 All versions
canonical linux-aws-5.3 All versions
canonical linux-aws-5.4 All versions
canonical linux-azure All versions
canonical linux-azure-4.15 All versions
canonical linux-azure-5.3 All versions
canonical linux-azure-5.4 All versions
canonical linux-azure-edge All versions
canonical linux-gcp All versions
canonical linux-gcp-4.15 All versions
canonical linux-gcp-5.3 All versions
canonical linux-gcp-5.4 All versions
canonical linux-gke-4.15 All versions
canonical linux-gke-5.4 All versions
canonical linux-gkeop-5.4 All versions
canonical linux-hwe All versions
canonical linux-hwe-5.4 All versions
canonical linux-hwe-edge All versions
canonical linux-ibm-5.4 All versions
canonical linux-kvm All versions
canonical linux-oem All versions
canonical linux-oracle All versions
canonical linux-oracle-5.0 All versions
canonical linux-oracle-5.3 All versions
canonical linux-oracle-5.4 All versions
canonical linux-raspi-5.4 All versions
canonical linux-aws-fips All versions
canonical linux-azure-fips All versions
canonical linux-fips All versions
canonical linux-gcp-fips All versions
canonical linux-aws-fips All versions
canonical linux-azure-fips All versions
canonical linux-fips All versions
canonical linux-gcp-fips All versions
canonical linux All versions
canonical linux-aws All versions
canonical linux-aws-5.11 All versions
canonical linux-aws-5.13 All versions
canonical linux-aws-5.15 All versions
canonical linux-aws-5.8 All versions
canonical linux-azure All versions
canonical linux-azure-5.11 All versions
canonical linux-azure-5.13 All versions
canonical linux-azure-5.15 All versions
canonical linux-azure-5.8 All versions
canonical linux-azure-fde All versions
canonical linux-azure-fde-5.15 All versions
canonical linux-bluefield All versions
canonical linux-gcp All versions
canonical linux-gcp-5.11 All versions
canonical linux-gcp-5.13 All versions
canonical linux-gcp-5.15 All versions
canonical linux-gcp-5.8 All versions
canonical linux-gke All versions
canonical linux-gke-5.15 All versions
canonical linux-gkeop All versions
canonical linux-gkeop-5.15 All versions
canonical linux-hwe-5.11 All versions
canonical linux-hwe-5.13 All versions
canonical linux-hwe-5.15 All versions
canonical linux-hwe-5.8 All versions
canonical linux-ibm All versions
canonical linux-ibm-5.15 All versions
canonical linux-intel-5.13 All versions
canonical linux-intel-iotg-5.15 All versions
canonical linux-iot All versions
canonical linux-kvm All versions
canonical linux-lowlatency-hwe-5.15 All versions
canonical linux-nvidia-tegra-5.15 All versions
canonical linux-oem-5.10 All versions
canonical linux-oem-5.13 All versions
canonical linux-oem-5.14 All versions
canonical linux-oem-5.6 All versions
canonical linux-oracle All versions
canonical linux-oracle-5.11 All versions
canonical linux-oracle-5.13 All versions
canonical linux-oracle-5.15 All versions
canonical linux-oracle-5.8 All versions
canonical linux-raspi All versions
canonical linux-raspi2 All versions
canonical linux-riscv All versions
canonical linux-riscv-5.11 All versions
canonical linux-riscv-5.15 All versions
canonical linux-riscv-5.8 All versions
canonical linux-xilinx-zynqmp All versions
canonical linux-aws-fips All versions
canonical linux-azure-fips All versions
canonical linux-fips All versions
canonical linux-gcp-fips All versions
canonical linux-aws-fips All versions
canonical linux-azure-fips All versions
canonical linux-fips All versions
canonical linux-gcp-fips All versions
canonical linux All versions
canonical linux-allwinner-5.19 All versions
canonical linux-aws All versions
canonical linux-aws-5.19 All versions
canonical linux-aws-6.2 All versions
canonical linux-aws-6.5 All versions
canonical linux-aws-6.8 All versions
canonical linux-azure All versions
canonical linux-azure-5.19 All versions
canonical linux-azure-6.2 All versions
canonical linux-azure-6.5 All versions
canonical linux-azure-6.8 All versions
canonical linux-azure-fde All versions
canonical linux-azure-fde-5.19 All versions
canonical linux-azure-fde-6.2 All versions
canonical linux-azure-fde-6.8 All versions
canonical linux-gcp All versions
canonical linux-gcp-5.19 All versions
canonical linux-gcp-6.2 All versions
canonical linux-gcp-6.5 All versions
canonical linux-gcp-6.8 All versions
canonical linux-gke All versions
canonical linux-gkeop All versions
canonical linux-hwe-5.19 All versions
canonical linux-hwe-6.2 All versions
canonical linux-hwe-6.5 All versions
canonical linux-hwe-6.8 All versions
canonical linux-ibm All versions
canonical linux-ibm-6.8 All versions
canonical linux-intel-iot-realtime All versions
canonical linux-intel-iotg All versions
canonical linux-kvm All versions
canonical linux-lowlatency All versions
canonical linux-lowlatency-hwe-5.19 All versions
canonical linux-lowlatency-hwe-6.2 All versions
canonical linux-lowlatency-hwe-6.5 All versions
canonical linux-lowlatency-hwe-6.8 All versions
canonical linux-nvidia All versions
canonical linux-nvidia-6.2 All versions
canonical linux-nvidia-6.5 All versions
canonical linux-nvidia-6.8 All versions
canonical linux-nvidia-tegra All versions
canonical linux-nvidia-tegra-igx All versions
canonical linux-oem-5.17 All versions
canonical linux-oem-6.0 All versions
canonical linux-oem-6.1 All versions
canonical linux-oem-6.5 All versions
canonical linux-oracle All versions
canonical linux-oracle-6.5 All versions
canonical linux-oracle-6.8 All versions
canonical linux-raspi All versions
canonical linux-realtime All versions
canonical linux-riscv All versions
canonical linux-riscv-5.19 All versions
canonical linux-riscv-6.5 All versions
canonical linux-riscv-6.8 All versions
canonical linux-starfive-5.19 All versions
canonical linux-starfive-6.2 All versions
canonical linux-starfive-6.5 All versions
canonical linux-xilinx-zynqmp All versions
canonical linux-bluefield All versions
canonical linux-aws-fips All versions
canonical linux-azure-fips All versions
canonical linux-fips All versions
canonical linux-gcp-fips All versions
canonical linux-aws-fips All versions
canonical linux-azure-fips All versions
canonical linux-fips All versions
canonical linux-gcp-fips All versions
canonical linux-intel-iot-realtime All versions
canonical linux-realtime All versions
canonical linux-realtime-6.8 All versions
canonical linux All versions
canonical linux-aws All versions
canonical linux-aws-6.14 All versions
canonical linux-aws-6.17 All versions
canonical linux-azure All versions
canonical linux-azure-6.11 All versions
canonical linux-azure-6.14 All versions
canonical linux-azure-6.17 All versions
canonical linux-azure-fde All versions
canonical linux-azure-fde-6.14 All versions
canonical linux-azure-fde-6.17 All versions
canonical linux-azure-nvidia All versions
canonical linux-azure-nvidia-6.14 All versions
canonical linux-gcp All versions
canonical linux-gcp-6.11 All versions
canonical linux-gcp-6.14 All versions
canonical linux-gcp-6.17 All versions
canonical linux-gke All versions
canonical linux-gkeop All versions
canonical linux-hwe-6.11 All versions
canonical linux-hwe-6.14 All versions
canonical linux-hwe-6.17 All versions
canonical linux-ibm All versions
canonical linux-lowlatency All versions
canonical linux-lowlatency-hwe-6.11 All versions
canonical linux-nvidia All versions
canonical linux-nvidia-6.11 All versions
canonical linux-nvidia-lowlatency All versions
canonical linux-nvidia-tegra All versions
canonical linux-oem-6.11 All versions
canonical linux-oem-6.14 All versions
canonical linux-oem-6.17 All versions
canonical linux-oem-6.8 All versions
canonical linux-oracle All versions
canonical linux-oracle-6.14 All versions
canonical linux-oracle-6.17 All versions
canonical linux-raspi All versions
canonical linux-raspi-realtime All versions
canonical linux-realtime All versions
canonical linux-riscv All versions
canonical linux-riscv-6.14 All versions
canonical linux-riscv-6.17 All versions
canonical linux-xilinx All versions
canonical linux-aws-fips All versions
canonical linux-azure-fips All versions
canonical linux-fips All versions
canonical linux-gcp-fips All versions
canonical linux-raspi-realtime All versions
canonical linux-realtime All versions
canonical linux-realtime-6.14 All versions
canonical linux All versions
canonical linux-aws All versions
canonical linux-azure All versions
canonical linux-azure-fde All versions
canonical linux-gcp All versions
canonical linux-oracle All versions
canonical linux-raspi All versions
canonical linux-realtime All versions
canonical linux-riscv All versions
Original title
In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix infinite loop caused by next_smb2_rcv_hdr_off reset in error paths The problem occurs when a signed request fails smb2...
Original description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix infinite loop caused by next_smb2_rcv_hdr_off reset in error paths The problem occurs when a signed request fails smb2 signature verification check. In __process_request(), if check_sign_req() returns an error, set_smb2_rsp_status(work, STATUS_ACCESS_DENIED) is called. set_smb2_rsp_status() set work->next_smb2_rcv_hdr_off as zero. By resetting next_smb2_rcv_hdr_off to zero, the pointer to the next command in the chain is lost. Consequently, is_chained_smb2_message() continues to point to the same request header instead of advancing. If the header's NextCommand field is non-zero, the function returns true, causing __handle_ksmbd_work() to repeatedly process the same failed request in an infinite loop. This results in the kernel log being flooded with "bad smb2 signature" messages and high CPU usage. This patch fixes the issue by changing the return value from SERVER_HANDLER_CONTINUE to SERVER_HANDLER_ABORT. This ensures that the processing loop terminates immediately rather than attempting to continue from an invalidated offset.
Published: 18 Feb 2026 · Updated: 13 Mar 2026 · First seen: 9 Mar 2026