Authenticated file destruction via missing handle permission check
Published Jul 25, 2026 · Updated Jul 25, 2026
Improper authorization in Linux Kernel ksmbd allows remote authenticated users to zero file data over SMB without write-data rights. In smb2_ioctl(), FSCTL_SET_ZERO_DATA checks only that the share is writable, then ksmbd_vfs_zero_data() calls vfs_fallocate() without verifying FILE_WRITE_DATA on the handle. A valid SMB session, writable-share access, and FILE_WRITE_ATTRIBUTES on the target are sufficient to erase selected ranges or an entire file, causing persistent data loss and service interruption.
Summary
What happened
Improper authorization in Linux Kernel ksmbd allows remote authenticated users to zero file data over SMB without write-data rights. In smb2_ioctl(), FSCTL_SET_ZERO_DATA checks only that the share is writable, then ksmbd_vfs_zero_data() calls vfs_fallocate() without verifying FILE_WRITE_DATA on the handle. A valid SMB session, writable-share access, and FILE_WRITE_ATTRIBUTES on the target are sufficient to erase selected ranges or an entire file, causing persistent data loss and service interruption.
The record
- CVE
- CVE-2026-64398
- Published
- Jul 25, 2026
- Updated
- Jul 25, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux Kernel
- Classifications
- CWE-266, T1485
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Jul 25, 2026CVE publishedPublication date reported by the CVE source.
- Jul 25, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <6.1.178
- Affected versionversion=0 <6.12.96
- Affected versionversion=0 <6.18.39
- Affected versionversion=0 <6.6.145
- Affected versionversion=0 <7.1.4
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <25377f369688dd0bd814dc8965ed26d44238ecaa
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <3072d82461f498c85daea8766e9d8bfbada31605
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <3320ba068198adc144c89d6661b805acce01735b
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <57f2042fd87d7ce8fc3ac8b6c176e554df68b1a7
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <ca53bb17f4e8232cfaece3953d3cef62c559b039
- Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <deffa929086d7902e30918adf3dd27ccfe9c08b1
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
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Public exploit references
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Technologies
Your stack
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Your stack
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