Improper access control in Linux kernel - CVE-2026-64398
Published: July 27, 2026
Vulnerability identifier: #VU139568
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-2026-64398
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to modify file data without the required file write permission.
The vulnerability exists due to improper access control in smb2_ioctl() when processing FSCTL_SET_ZERO_DATA requests. A remote user can use a handle opened with only FILE_WRITE_ATTRIBUTES to zero file data and modify file contents without the required FILE_WRITE_DATA right.
The issue affects ksmbd, and the advisory states it was reproduced by an authenticated SMB client using a handle that was granted FILE_WRITE_ATTRIBUTES but not FILE_WRITE_DATA.
Affected software
Linux kernel
How to mitigate CVE-2026-64398
Install security update from vendor's repository.
Linux kernel - update to 7.0 rc3
External References
- https://git.kernel.org/stable/c/25377f369688dd0bd814dc8965ed26d44238ecaa
- https://git.kernel.org/stable/c/3072d82461f498c85daea8766e9d8bfbada31605
- https://git.kernel.org/stable/c/3320ba068198adc144c89d6661b805acce01735b
- https://git.kernel.org/stable/c/57f2042fd87d7ce8fc3ac8b6c176e554df68b1a7
- https://git.kernel.org/stable/c/ca53bb17f4e8232cfaece3953d3cef62c559b039
- https://git.kernel.org/stable/c/deffa929086d7902e30918adf3dd27ccfe9c08b1