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.
Affected versions
Fixed in
6.1.178,
6.6.145,
6.12.96,
6.18.39,
7.1.4,
7.2-rc1
and their respective stable series.
References
6 totalFrequently asked questions
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What is CVE-2026-64399?
CVE-2026-64399 is a unscored severity Linux kernel vulnerability . CVE-2026-64399 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
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Is there a patch available for CVE-2026-64399?
Yes. CVE-2026-64399 has been patched. Fixed versions include 6.1.178, 6.6.145, 6.12.96 and others.
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Is CVE-2026-64399 actively exploited?
No. CVE-2026-64399 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.