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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
| Vendor | Product | Affected versions | Fix 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.
- https://ubuntu.com/security/CVE-2026-23220 Third Party Advisory
- https://www.cve.org/CVERecord?id=CVE-2026-23220 Third Party Advisory
- https://git.kernel.org/stable/c/5accdc5b7f28a81bbc5880ac0b8886e60c86e8c8 Third Party Advisory
- https://git.kernel.org/stable/c/71b5e7c528315ca360a1825a4ad2f8ae48c5dc16 Third Party Advisory
- https://git.kernel.org/stable/c/9135e791ec2709bcf0cda0335535c74762489498 Third Party Advisory
- https://git.kernel.org/stable/c/f7b1c2f5642bbd60b1beef1f3298cbac81eb232c Third Party Advisory
Published: 18 Feb 2026 · Updated: 13 Mar 2026 · First seen: 9 Mar 2026