CVE-2026-68457
CriticalCVSS 9.1Exploitation Probability (EPSS)
Low risk7th percentile - higher than 7% of all known CVEs
Summary
In the Linux kernel ksmbd (SMB) server, FSCTL operations such as SET_SPARSE, SET_ZERO_DATA, and SET_COMPRESSION operate on an open SMB handle but call VFS helpers with the current ksmbd worker credentials. This can lead to revalidation of inode permissions, ownership, and LSM policy independently of the SMB handle access mask. The fix runs each operation with the credentials captured in the target file when the handle was opened.
Risk Assessment
The vulnerability could allow unauthorized access to files or modification of data, bypassing SMB access controls, potentially leading to confidentiality and integrity breaches.
Recommendation
It is recommended to update the Linux kernel to a version containing the fix that uses opener credentials for FSCTL operations in ksmbd.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: ksmbd: use opener credentials for FSCTL mutations SET_SPARSE, SET_ZERO_DATA and SET_COMPRESSION operate on an open SMB handle but call VFS xattr, fallocate or fileattr helpers with the current ksmbd worker credentials. Those helpers can revalidate inode permissions, ownership and LSM policy independently of the SMB handle access mask. Run each operation with the credentials captured in the target file when the handle was opened. Keep credential handling local to these single-file FSCTLs rather than applying session credentials to the complete IOCTL handler, which also contains handle-less and multi-handle operations.