Vulnerability Description
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.
CVSS Score
CRITICAL
References
- https://git.kernel.org/stable/c/388e4139db27a9e3612c9d356b826f5b1ff6a9e3
- https://git.kernel.org/stable/c/620d133d469295ee7c017ca6aafac335f65c4a5a
- https://git.kernel.org/stable/c/9b9cf7e65cbeaae1b6636144bacee611cdd7a5d6
- https://git.kernel.org/stable/c/baae7b39673ec21073a25e3d14f8feaada01d5df
- https://git.kernel.org/stable/c/bf460ad5958d506492de4524a656439da3f99c51
- https://git.kernel.org/stable/c/c917e4522d251071dde9871b9142d8ea1186ebfe
FAQ
What is CVE-2026-64399?
CVE-2026-64399 is a vulnerability with a CVSS score of 9.8 (CRITICAL). 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() overwrite...
How severe is CVE-2026-64399?
CVE-2026-64399 has been rated CRITICAL with a CVSS base score of 9.8/10. This is considered a critical vulnerability requiring immediate attention.
Is there a patch for CVE-2026-64399?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.