Improper access control in Linux kernel - CVE-2026-64399
Published: July 27, 2026
Vulnerability identifier: #VU139569
CSH Severity: Medium
CVSS v4: 7.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-64399
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to overwrite file data.
The vulnerability exists due to improper access control in the FSCTL_DUPLICATE_EXTENTS_TO_FILE arm of smb2_ioctl() when processing SMB ioctl requests that clone file ranges. A remote user can use the operation on a read-only share or with a destination handle lacking FILE_WRITE_DATA permission to overwrite file data.
The issue affects destination files through vfs_clone_file_range() and can be triggered with a handle opened with only FILE_WRITE_ATTRIBUTES.
Affected software
Linux kernel
How to mitigate CVE-2026-64399
Install security update from vendor's repository.
Linux kernel - update to 7.0 rc3
External 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