CVE-2026-64399

Updated on 25 Jul 2026

Severity

9.8 Critical severity

Details

CVSS score
9.8

Overview

About vulnerability

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE

The FSCTL_DUPLICATE_EXTENTS_TO_FILE arm of smb2_ioctl() overwrites the destination file’s data via vfs_clone_file_range() with neither the share-level KSMBD_TREE_CONN_FLAG_WRITABLE check nor a per-handle fp->daccess check that the other write-bearing arms carry. A client can overwrite destination data on a read-only share, or from a handle opened with only FILE_WRITE_ATTRIBUTES (which still yields an FMODE_WRITE filp). FILE_WRITE_ATTRIBUTES-only destination handle overwrote the file’s data via the clone. Add both checks, matching the FSCTL_SET_SPARSE permission fix; require FILE_WRITE_DATA since this writes data.

Details

KernelCare state

Live-patch status from KernelCare for each operating system.

Operating system Status Covered kernels
Debian 12 Planned