CVE-2026-64399
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.
CSIRTS triage
- What
- This vulnerability involves adding permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE in ksmbd.
- Who is affected
- Deployments of the Linux kernel using ksmbd are affected.
- Urgency
- Remediation is necessary to prevent unauthorized access, though exploitation is not confirmed.
- Action
- Apply the latest kernel patches that address this issue.
AI-assisted analysis generated from the source advisory — verify against the original.
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Exploitation outlook
- Low exploitation risk0.49% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 40% of all EPSS-scored CVEs.
Advisory coverage (2)
External references
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