CVE-2026-68457

Received Received - Intake

ksmbd FSCTL Permission Bypass via Credential Handling

Publication date: 2026-08-15

Last updated on: 2026-08-18

Assigner: kernel.org

Description

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.

CVSS Scores

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Meta Information

Published

2026-08-15

Last Modified

2026-08-18

Generated

2026-09-04

AI Q&A

2026-08-15

EPSS Evaluated

2026-09-03

NVD

CVE-2026-68457

EUVD

EUVD-2026-59079

Affected Vendors & Products

Vendor	Product	Version / Range
linux_kernel	ksmbd	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability in the Linux kernel involves incorrect credential handling in the ksmbd SMB server. Operations like SET_SPARSE, SET_ZERO_DATA, and SET_COMPRESSION use the current worker credentials instead of the credentials from when the SMB handle was opened. This could allow unauthorized changes to file attributes or permissions.

Detection Guidance

This vulnerability is specific to the Linux kernel's ksmbd implementation and involves improper credential handling during SMB FSCTL operations. Detection requires checking kernel logs for related errors or monitoring SMB traffic for anomalies in FSCTL requests. No direct detection commands are provided in the context.

Impact Analysis

An attacker with access to the SMB server could exploit this to modify file attributes or permissions without proper authorization. This might lead to unauthorized data access, corruption, or denial of service on affected systems.

Compliance Impact

This vulnerability could violate compliance requirements by allowing unauthorized access or modification of sensitive data. Organizations using affected Linux kernel versions may fail audits or face penalties for non-compliance with data protection standards.

Mitigation Strategies

Update the Linux kernel to the latest patched version to resolve the ksmbd credential handling issue in FSCTL mutations.

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