CVE Catalog

CVE-2026-64398

HighCVSS 8.1
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.46%

38th percentile - higher than 38% of all known CVEs

Summary

In the Linux kernel, the ksmbd filesystem lacks a permission check for the FSCTL_SET_ZERO_DATA operation. An authenticated SMB client can use a handle opened only with FILE_WRITE_ATTRIBUTES to zero file data without FILE_WRITE_DATA rights.

Risk Assessment

An attacker can destroy file data without proper permissions, leading to data integrity loss.

Recommendation

Apply the Linux kernel patch that adds a FILE_WRITE_DATA permission requirement for the FSCTL_SET_ZERO_DATA operation.

Other vulnerabilities in Linux kernel

See all
Original NVD description (English source)

In the Linux kernel, the following vulnerability has been resolved: ksmbd: add a permission check for FSCTL_SET_ZERO_DATA FSCTL_SET_ZERO_DATA in smb2_ioctl() destroys file data via ksmbd_vfs_zero_data() -> vfs_fallocate(PUNCH_HOLE/ZERO_RANGE) after checking only the share-level KSMBD_TREE_CONN_FLAG_WRITABLE, with no per-handle access check. A handle opened with only FILE_WRITE_ATTRIBUTES still yields an FMODE_WRITE filp (FILE_WRITE_ATTRIBUTES is part of FILE_WRITE_DESIRE_ACCESS_LE, so smb2_create_open_flags() opens it O_WRONLY), so the vfs_fallocate FMODE_WRITE check does not stop it; only the missing fp->daccess gate would. Reproduced on mainline 7.1-rc7 with KASAN by an authenticated SMB client: a FILE_WRITE_ATTRIBUTES-only handle zeroed 4096 bytes of file data it had no FILE_WRITE_DATA right to (6/6; a FILE_READ_DATA-only handle was correctly denied). This is the unfixed sibling of commit cc57232cae23 ("ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE"). Because SET_ZERO_DATA writes data (not an attribute), require FILE_WRITE_DATA.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS